Component derating checker
Check each part's applied stress against its rating and the derating rule for its type, and list the parts that pass, fail or sit close to the limit.
ReliabilityFree to useHow it worksSourcesWhere it helps
Fills the inputs below with typical figures. Replace any of them with your own.
- Parts that fail
- 0
- of 18 checked
- Close to the limit
- 2
- Within 10% of the allowed value
- Pass
- 16
- 89% of checked
- Highest use of the allowed value
- 94%
- C2 voltage
Bars show applied over rated. The note gives the ratio the rule allows. For a temperature the ratio is in degrees Celsius.
- C2, voltage40%allowed 43%, close to limit
- D1, reverse voltage63%allowed 70%, close to limit
- D1, junction temperature65%allowed 73%, pass
- L1, hot-spot or contact temperature77%allowed 87%, pass
- J1, current44%allowed 50%, pass
- U1, output current70%allowed 80%, pass
- Q1, junction temperature64%allowed 73%, pass
- Q1, gate to source voltage50%allowed 60%, pass
- K1, current60%allowed 72%, pass
- Y1, power or drive level20%allowed 25%, pass
- U2, supply voltage71%allowed 90%, pass
- D1, current38%allowed 50%, pass
- U1, supply voltage60%allowed 80%, pass
- R1, power or drive level44%allowed 60%, pass
- Q1, voltage52%allowed 75%, pass
- Q1, current49%allowed 75%, pass
- R2, voltage37%allowed 80%, pass
- C1, voltage28%allowed 60%, pass
Show the data as a table
| Item | Stress ratio |
|---|---|
| C2, voltage | 40% |
| D1, reverse voltage | 63% |
| D1, junction temperature | 65% |
| L1, hot-spot or contact temperature | 77% |
| J1, current | 44% |
| U1, output current | 70% |
| Q1, junction temperature | 64% |
| Q1, gate to source voltage | 50% |
| K1, current | 60% |
| Y1, power or drive level | 20% |
| U2, supply voltage | 71% |
| D1, current | 38% |
| U1, supply voltage | 60% |
| R1, power or drive level | 44% |
| Q1, voltage | 52% |
| Q1, current | 49% |
| R2, voltage | 37% |
| C1, voltage | 28% |
Sign in to save your inputs and come back to them later.
| Part and stress | Type | Stress ratio | Allowed ratio | Headroom (ratio points) | Headroom as share of allowed | Largest value allowed | Status | Rule from |
|---|---|---|---|---|---|---|---|---|
| C2, voltage | Tantalum capacitor | 40.0% | 42.5% | 0.025 | 5.9% | 21.25 V | Close to limit | NASA EEE-INST-002 (2003), capacitors, Table 4 |
| D1, reverse voltage | Diode | 63.3% | 70.0% | 0.0667 | 9.5% | 42 V | Close to limit | NASA EEE-INST-002 (2003), discrete semiconductors, diodes, Table 4 |
| D1, junction temperature | Diode | 65.3% | 73.3% | 0.08 | 10.9% | 110 °C | Pass | NASA EEE-INST-002 (2003), discrete semiconductors, diodes, Table 4 note |
| L1, hot-spot or contact temperature | Inductor or transformer | 77.4% | 87.1% | 0.0968 | 11.1% | 135 °C | Pass | ECSS-Q-30-11A (2006), clause 6.18 |
| J1, current | Connector | 44.0% | 50.0% | 0.06 | 12.0% | 2.5 A | Pass | ECSS-Q-30-11A (2006), clause 6.11 |
| U1, output current | Integrated circuit, linear | 70.0% | 80.0% | 0.1 | 12.5% | 0.8 A | Pass | NASA EEE-INST-002 (2003), monolithic microcircuits, Table 4 |
| Q1, junction temperature | Transistor (bipolar or MOSFET) | 64.0% | 73.3% | 0.0933 | 12.7% | 110 °C | Pass | NASA EEE-INST-002 (2003), discrete semiconductors, transistors, Table 4 note |
| Q1, gate to source voltage | Transistor (bipolar or MOSFET) | 50.0% | 60.0% | 0.1 | 16.7% | 12 V | Pass | NASA EEE-INST-002 (2003), discrete semiconductors, transistors, Table 4 |
| K1, current | Relay | 60.0% | 72.3% | 0.123 | 17.0% | 1.445 A | Pass | NASA EEE-INST-002 (2003), relays, Table 4 |
| Y1, power or drive level | Crystal | 20.0% | 25.0% | 0.05 | 20.0% | 0.025 W | Pass | NASA EEE-INST-002 (2003), crystals, Table 4 |
| U2, supply voltage | Integrated circuit, digital | 71.4% | 90.0% | 0.186 | 20.6% | 6.3 V | Pass | NASA EEE-INST-002 (2003), monolithic microcircuits, Table 4 |
| D1, current | Diode | 38.0% | 50.0% | 0.12 | 24.0% | 5 A | Pass | NASA EEE-INST-002 (2003), discrete semiconductors, diodes, Table 4 |
| U1, supply voltage | Integrated circuit, linear | 60.0% | 80.0% | 0.2 | 25.0% | 16 V | Pass | NASA EEE-INST-002 (2003), monolithic microcircuits, Table 4 |
| R1, power or drive level | Resistor | 44.0% | 60.0% | 0.16 | 26.7% | 0.15 W | Pass | NASA EEE-INST-002 (2003), resistors, Table 4 |
| Q1, voltage | Transistor (bipolar or MOSFET) | 52.0% | 75.0% | 0.23 | 30.7% | 75 V | Pass | NASA EEE-INST-002 (2003), discrete semiconductors, transistors, Table 4 |
| Q1, current | Transistor (bipolar or MOSFET) | 49.0% | 75.0% | 0.26 | 34.7% | 15 A | Pass | NASA EEE-INST-002 (2003), discrete semiconductors, transistors, Table 4 |
| R2, voltage | Resistor | 37.3% | 80.0% | 0.427 | 53.3% | 60 V | Pass | NASA EEE-INST-002 (2003), resistors, Table 4 |
| C1, voltage | Ceramic capacitor | 28.0% | 60.0% | 0.32 | 53.3% | 60 V | Pass | NASA EEE-INST-002 (2003), capacitors, Table 4 |
- Resistor, power or drive level (solid line, circles)
- Tantalum capacitor, voltage (dashed line, squares)
- Relay, current (dotted line, triangles)
Show the data as a table
| Ambient or hot-spot temperature (°C), 25 to 155 | Resistor, power or drive level | Tantalum capacitor, voltage | Relay, current |
|---|---|---|---|
| 25 | 60 | 50 | 85 |
| 40 | 60 | 50 | 72.3 |
| 55 | 60 | 50 | 72.3 |
| 70 | 60 | 50 | 72.3 |
| 85 | 41.3 | 42.5 | 59.5 |
| 100 | 22.5 | 35 | 59.5 |
| 115 | 3.75 | 30 | 59.5 |
| 125 | 0 | 30 | 59.5 |
| 140 | 0 | 30 | 59.5 |
| 155 | 0 | 30 | 59.5 |
| Part type | Parameter | Allowed | Temperature | Source | Where | Note |
|---|---|---|---|---|---|---|
| Resistor | Power or drive level | 60% of rating | Falls with temperature: 60% at 70 °C, 0% at 118 °C | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), resistors, Table 4 | Film chip style: full allowed share to 70 °C, falling in a straight line to nothing at the style's zero-power temperature (118 °C here). Other styles differ; use the custom set for them. |
| Resistor | Voltage | 80% of rating | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), resistors, Table 4 | Also keep below the voltage that gives the derated power. | |
| Ceramic capacitor | Voltage | 60% of rating | Data to 110 °C | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), capacitors, Table 4 | Applies to the sum of DC and peak AC voltage, up to 110 °C. |
| Tantalum capacitor | Voltage | 50% of rating | Falls with temperature: 50% at 70 °C, 30% at 110 °C | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), capacitors, Table 4 | Solid tantalum: full allowed share to 70 °C, falling in a straight line to 110 °C. Keep circuit surge current limited. |
| Tantalum capacitor | Reverse voltage | 75% of rating | ECSS derating | ECSS-Q-30-11A (2006), clause 6.3 | ||
| Tantalum capacitor | Surge current | 75% of rating | ECSS derating | ECSS-Q-30-11A (2006), clause 6.3 | Of the surge current the rated voltage, ESR and series resistance allow. | |
| Aluminium electrolytic capacitor | Voltage | 80% of rating | Hub editorial | Hub editorial | The space documents do not cover aluminium electrolytics. 80% of rated voltage is common practice; follow the maker's life curves. | |
| Aluminium electrolytic capacitor | Ripple current | 80% of rating | Hub editorial | Hub editorial | Of the ripple rating at the hot-spot temperature. Ripple heating sets the life. | |
| Diode | Reverse voltage | 70% of rating | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), discrete semiconductors, diodes, Table 4 | ||
| Diode | Current | 50% of rating | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), discrete semiconductors, diodes, Table 4 | ||
| Diode | Surge current | 50% of rating | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), discrete semiconductors, diodes, Table 4 | ||
| Diode | Power or drive level | 50% of rating | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), discrete semiconductors, diodes, Table 4 | NASA lists this for varactor, voltage reference, suppressor and similar diodes. | |
| Diode | Junction temperature | at most 125 °C, and 40 °C below the rated temperature | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), discrete semiconductors, diodes, Table 4 note | The lower of 125 °C and 40 °C below the maker's maximum. | |
| Transistor (bipolar or MOSFET) | Power or drive level | 60% of rating | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), discrete semiconductors, transistors, Table 4 | Check the safe operating area as well. | |
| Transistor (bipolar or MOSFET) | Current | 75% of rating | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), discrete semiconductors, transistors, Table 4 | ||
| Transistor (bipolar or MOSFET) | Voltage | 75% of rating | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), discrete semiconductors, transistors, Table 4 | Worst case of DC, AC and transient voltage. Power MOSFETs in radiation need extra care. | |
| Transistor (bipolar or MOSFET) | Gate to source voltage | 60% of rating | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), discrete semiconductors, transistors, Table 4 | ||
| Transistor (bipolar or MOSFET) | Junction temperature | at most 125 °C, and 40 °C below the rated temperature | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), discrete semiconductors, transistors, Table 4 note | ||
| Integrated circuit, digital | Supply voltage | 90% of rating | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), monolithic microcircuits, Table 4 | For devices under 5 V NASA allows the maker's recommended conditions. | |
| Integrated circuit, digital | Output current | 80% of rating | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), monolithic microcircuits, Table 4 | ||
| Integrated circuit, digital | Power or drive level | 80% of rating | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), monolithic microcircuits, Table 4 | ||
| Integrated circuit, digital | Junction temperature | at most 110 °C, and 40 °C below the rated temperature | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), monolithic microcircuits, Table 4 note | The lower of 110 °C and 40 °C below the maker's maximum. | |
| Integrated circuit, linear | Supply voltage | 80% of rating | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), monolithic microcircuits, Table 4 | ||
| Integrated circuit, linear | Output current | 80% of rating | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), monolithic microcircuits, Table 4 | ||
| Integrated circuit, linear | Power or drive level | 75% of rating | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), monolithic microcircuits, Table 4 | ||
| Integrated circuit, linear | Junction temperature | at most 110 °C, and 40 °C below the rated temperature | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), monolithic microcircuits, Table 4 note | ||
| Connector | Voltage | 75% of rating | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), connectors, Table 5 | Of the working voltage at sea level, or a quarter of the dielectric withstanding voltage, whichever is lower. Enter the lower figure as the rating. | |
| Connector | Current | 50% of rating | ECSS derating | ECSS-Q-30-11A (2006), clause 6.11 | NASA ties contact current to a wire-size table instead of a fixed share. | |
| Connector | Hot-spot or contact temperature | 25 °C below the rated temperature | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), connectors, Table 5 | ||
| Relay | Current | 85% of rating | Falls with temperature: 85% at 39 °C, 72.3% at 40 °C, 72.3% at 84 °C, 59.5% at 85 °C | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), relays, Table 4 | Resistive load, more than 10 operations an hour. NASA multiplies a load, a cycle-rate and a temperature factor; the temperature steps are shown as sharp ramps. |
| Relay | Inductive load current | 40% of rating | ECSS derating | ECSS-Q-30-11A (2006), clause 6.25 | Of the resistive rating when no inductive rating is given (50% of an inductive rating if there is one). | |
| Relay | Motor load current | 20% of rating | ECSS derating | ECSS-Q-30-11A (2006), clause 6.25 | Of the resistive rating when no motor rating is given. | |
| Inductor or transformer | Voltage | 50% of rating | ECSS derating | ECSS-Q-30-11A (2006), clause 6.18 | Of the insulation test voltage, winding to winding and winding to case. | |
| Inductor or transformer | Hot-spot or contact temperature | 20 °C below the rated temperature | ECSS derating | ECSS-Q-30-11A (2006), clause 6.18 | Hot-spot temperature, which is ambient plus temperature rise plus an allowance for hot spots. | |
| Optocoupler | Current | 50% of rating | ECSS derating | ECSS-Q-30-11A (2006), clause 6.33 | LED forward current, when the maker gives no recommended value. NASA gives no separate optocoupler table. | |
| Optocoupler | Reverse voltage | 75% of rating | ECSS derating | ECSS-Q-30-11A (2006), clause 6.33 | ||
| Optocoupler | Output current | 80% of rating | ECSS derating | ECSS-Q-30-11A (2006), clause 6.33 | Phototransistor collector current. | |
| Optocoupler | Voltage | 75% of rating | ECSS derating | ECSS-Q-30-11A (2006), clause 6.33 | Collector to emitter voltage. | |
| Optocoupler | Junction temperature | at most 110 °C, and 40 °C below the rated temperature | ECSS derating | ECSS-Q-30-11A (2006), clause 6.33 | ||
| Crystal | Power or drive level | 25% of rating | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), crystals, Table 4 | Drive level. Derate either power or current, not both. | |
| Crystal | Current | 50% of rating | NASA EEE-INST-002 | NASA EEE-INST-002 (2003), crystals, Table 4 |
How it works
Derating keeps the stress on a part below its rating so it ages slowly and survives surprises. This tool takes each part's rated and applied value, finds the derating rule for that part type and parameter, and reports the stress ratio, the allowed ratio, the headroom and a verdict: pass, close to the limit or fail.
- Stress ratio. The stress ratio is the applied value as a share of the part's rating, for voltage, current or power. For a temperature it is the applied temperature over the rated temperature in degrees Celsius, and the verdict uses the temperature limit instead.
stress ratio = applied value / rated value - Allowed ratio. Each rule gives the share of the rating the applied value may use. Some rules fall in a straight line once the part is hotter than a knee temperature, until they reach a lower share (or nothing) at a hot temperature. An optional extra derating factor tightens every voltage, current and power rule together.
allowed ratio = rule fraction x extra factor; above the knee T1: fraction(T) = f1 − (f1 − f2) x (T − T1) / (T2 − T1), held at f2 above T2 - Temperature limits. A temperature rule is a limit: the lower of an absolute cap and the rated temperature less a fixed number of degrees. The allowed ratio is that limit over the rated temperature.
limit = lower of (cap, rated temperature − offset); allowed ratio = limit / rated temperature - Headroom and verdict. The allowed value is the allowed ratio times the rating (or the temperature limit). Headroom is what is left under it. A part fails when the applied value is above the allowed value, is close to the limit when the headroom share is under the band (10% unless you change it), and otherwise passes.
allowed value = allowed ratio x rated value; headroom = allowed value − applied value; headroom share = headroom / allowed value; fail if headroom share < 0, close if < band, else pass - Rule sets. The Hub generic set follows the typical fractions of the NASA parts derating instructions and borrows the ECSS figure where NASA gives none. The ESA style set swaps in the ECSS figures where they differ. The commercial set is the Hub's own relaxed editorial figures. A custom set lets you override any rule for your own policy.
Assumptions
- Rated and applied values are entered in the same unit for each part; the ratio does not depend on the unit. Temperatures are in degrees Celsius.
- The applied value is the worst case in service: for a voltage, the sum of DC, ripple and transient peaks; for a temperature, the junction or hot-spot temperature at the worst ambient.
- Each row checks one parameter of one part. A part has several stresses, so enter one row for each, sharing a reference.
- A temperature in a row is the ambient or case temperature that sets the allowed share for power, voltage and current rules with a temperature fall. Leave it empty for a rule that does not fall with temperature.
- The rules are typical fractions written in the Hub's own words. Each names where its figure comes from; the commercial figures and the aluminium electrolytic figures are editorial.
Limits and warnings
- A project's own derating requirement, tailored by the customer, overrides any generic set. Check the clause in the edition your project cites.
- The checker is not a substitute for a full parts stress analysis: it does not check safe operating area, pulse and transient ratings, life curves, radiation effects, or part-specific rules such as the series resistance needed for tantalum capacitors.
- The ECSS figures were read from the 2006 edition of the ECSS derating standard. The current edition is ECSS-Q-ST-30-11C Rev. 2 (June 2021), and ECSS gives many families as charts that depend on temperature and mission length, which the ESA style set does not reproduce. Confirm any figure you rely on against the current edition.
- The NASA instructions are the May 2003 issue. NASA has been moving to a newer parts standard, so check which one your programme cites.
- Resistor temperature curves vary by style. The generic curve is for a film chip resistor; use the custom set for wirewound, precision and other styles.
Sources
The methods and default figures rest on these public sources. The wording here is our own; read the source for its full text.
- Instructions for EEE Parts Selection, Screening, Qualification, and Derating (EEE-INST-002), NASA/TP-2003-212242 (opens in a new tab), NASA Goddard Space Flight Center, May 2003. Table 4 of each part section (resistors, capacitors, discrete semiconductors, microcircuits, relays, magnetics, crystals) and Table 5 for connectors. Typical fractions only; none of the tables or text is copied.
- ECSS-Q-30-11A: Derating EEE components (opens in a new tab), European Cooperation for Space Standardization (ECSS), ESA-ESTEC, 24 April 2006. Clause 6 load ratios used for the figures that NASA does not give and for the ESA style set. Read from the ESCIES-hosted copy.
- ECSS-Q-ST-30-11C Rev. 2: Derating EEE components (opens in a new tab), European Cooperation for Space Standardization (ECSS), 23 June 2021. The current edition, which supersedes Rev. 1 of October 2011. Named so you can check each figure against it; the text of this edition was not available to read when the tool was built.
Where it helps
The lifecycle stages this tool serves: 4 stages in 3 lifecycles.
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Method notev1Formula, ranges, sources and limits
Checks each part's applied stress against its rating and the derating rule for its type and parameter, and counts the parts that pass, sit close to the limit or fail.
Formula
stress ratio = applied value / rated value; allowed ratio = rule fraction x extra factor; above the knee T1: fraction(T) = f1 − (f1 − f2) x (T − T1) / (T2 − T1), held at f2 above T2; limit = lower of (cap, rated temperature − offset); allowed ratio = limit / rated temperature; allowed value = allowed ratio x rated value; headroom = allowed value − applied value; headroom share = headroom / allowed value; fail if headroom share < 0, close if < band, else pass
| Input | Unit | Range it holds for | Comes from |
|---|---|---|---|
| Rule set | choice | hub, ecss, commercial, custom | Your figure |
| Base set under custom rules | choice | hub, ecss, commercial | Your figure |
| Close-to-limit band | % of the allowed value | 0 to 50 | Your figure |
| Extra derating factor | % (100 for none) | 1 to 100 | Your figure |
Outputs: Parts checked (parts); Parts that pass (parts); Parts close to the limit (parts); Parts that fail (parts); Highest applied over allowed (fraction).
Assumptions
- Rated and applied values are entered in the same unit for each part; the ratio does not depend on the unit. Temperatures are in degrees Celsius.
- The applied value is the worst case in service: for a voltage, the sum of DC, ripple and transient peaks; for a temperature, the junction or hot-spot temperature at the worst ambient.
- Each row checks one parameter of one part. A part has several stresses, so enter one row for each, sharing a reference.
- A temperature in a row is the ambient or case temperature that sets the allowed share for power, voltage and current rules with a temperature fall. Leave it empty for a rule that does not fall with temperature.
- The rules are typical fractions written in the Hub's own words. Each names where its figure comes from; the commercial figures and the aluminium electrolytic figures are editorial.
Uncertainty: The arithmetic is exact; the verdict is only as good as the applied stress entered and the rule chosen. A part within a few per cent of a limit should be treated as a judgement, since stress values are themselves estimates.
Known limits
- A project's own derating requirement, tailored by the customer, overrides any generic set. Check the clause in the edition your project cites.
- The checker is not a substitute for a full parts stress analysis: it does not check safe operating area, pulse and transient ratings, life curves, radiation effects, or part-specific rules such as the series resistance needed for tantalum capacitors.
- The ECSS figures were read from the 2006 edition of the ECSS derating standard. The current edition is ECSS-Q-ST-30-11C Rev. 2 (June 2021), and ECSS gives many families as charts that depend on temperature and mission length, which the ESA style set does not reproduce. Confirm any figure you rely on against the current edition.
- The NASA instructions are the May 2003 issue. NASA has been moving to a newer parts standard, so check which one your programme cites.
- Resistor temperature curves vary by style. The generic curve is for a film chip resistor; use the custom set for wirewound, precision and other styles.
Where the method comes from
The Hub's own stress-ratio check. The rule fractions are typical figures read from NASA EEE-INST-002 and the ECSS derating standard, restated as short rules; the commercial set is editorial.
Reference example, checked by test: Worked example in this method note: the space-grade DC-DC converter board preset (18 stresses on 14 parts) against the Hub generic rules, hand-worked in the tool's unit test. Parts checked 18; Parts that pass 16; Parts close to the limit 2; Parts that fail 0; Highest applied over allowed 0.9412.
Versions
- v1 (2026-10-25): First version, built from the tool idea.
Terms on this page
- Derating
- Applying a multiplicative factor to cell and net delays to model variation or guard band, typically slowing the launch path and speeding the capture path for setup and the reverse for hold.
- ECSS
- European Cooperation for Space Standardization (ECSS): the body, formed by the European Space Agency, national agencies and industry, that publishes the standards used on European space projects, i...
- Chip
- The everyday word for a finished integrated circuit, used loosely for both the bare die and the packaged part sold to a customer.
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