Testing & Measurement calculator
Shunt Calculator
A 100 A, 75 mV DC shunt has a nominal resistance of 0.75 mOhm and dissipates 7.5 W at full scale; a 50 mV meter on that same shunt reaches full scale at about 66.7 A. This page is the testing-side sibling of the Current Shunt Calculator. It does not try to redesign every shunt workflow. Instead, it stays on three practical jobs: turning a shunt nameplate into nominal resistance and power, comparing measured current and measured mV drop against the expected nameplate behavior, and checking whether a meter input is actually matched to the shunt millivolt rating.
Updated July 10, 2026
A 100 A, 75 mV shunt has a nominal resistance of 0.75 mOhm and dissipates 7.5 W at its nameplate current.
R = V ÷ I | 0.075 V ÷ 100 A = 0.00075 ohm, and P = I x V = 100 x 0.075 = 7.5 W.
Choose the nameplate, measured-drop, or meter-match mode below to verify an existing DC shunt instead of sizing a new one from scratch
Calculator Inputs
Quick Presets
Calculation Results
Enter values above to see calculation results
Field kit
Bench kit for shunt sizing
Use the calculated drop and current values to compare shunt parts and measurement tools for a controlled setup.
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Calculation history
Example Calculations
How to Use
When to use this page instead of the Current Shunt Calculator
Use this route when you already have a real shunt on the bench or in the field and need to verify it. If you are selecting a new DC shunt from a target current and target millivolt drop, the Current Shunt Calculator is the design-side page.
1. Pick the verification mode that matches the task
- Nameplate Resistance and Power converts the rated current and rated mV drop into nominal resistance and full-scale loss.
- Measured Current and Drop Check compares an actual test reading against the expected nameplate behavior and reports error plus a correction factor.
- Meter-to-Shunt Compatibility checks whether the meter full-scale mV input really matches the shunt rating.
2. Use the right inputs for the job
- Rated Shunt Current and Rated Shunt Drop come from the shunt nameplate, for example 100 A and 75 mV.
- Measured Test Current and Measured Shunt Drop are only for the field-verification mode.
- Meter Full-Scale Drop is only for the meter-match mode and should be the mV input required by the panel meter, transducer, or display.
- Allowed Drop Error is the tolerance band you want to use when deciding whether the measured drop is close enough to the expected value.
3. Read the main outputs correctly
- Nominal Shunt Resistance is derived from the nameplate using R = V / I.
- Rated Full-Scale Loss is the power the shunt dissipates at nameplate current and nameplate mV drop.
- Drop Error compares the measured shunt drop with the expected drop at the same current.
- Meter Correction Factor is useful when a display is calibrated to the shunt nameplate but the measured shunt drop does not line up perfectly.
- Current at Meter Full Scale shows how much actual current will flow when a given meter mV input reaches full scale on the selected shunt.
Worked 100 A, 75 mV example
| Item | Calculation | Result |
|---|---|---|
| Nominal resistance | 0.075 V / 100 A | 0.75 mOhm |
| Full-scale loss | 100 A x 0.075 V | 7.5 W |
| 50 mV meter match | 100 A x 50 / 75 | 66.7 A at meter full scale |
Field-check reminders that still matter
- Use Kelvin sense points at the shunt terminals. Lead resistance and clip placement can overwhelm a low-millivolt measurement.
- This route assumes a DC resistive shunt. It does not model AC current transformers, Hall sensors, isolated transducers, or waveform-dependent behavior.
- High-current shunts still need safe current sources, proper busbar hardware, and a real thermal review before a bench result is treated as a commissioning acceptance.
Common Applications
More applications. Open to review 2 additional use cases.
Frequently Asked Questions
How do I calculate the resistance of a current shunt from its nameplate?
Use R = V / I. A 100 A, 75 mV shunt is 0.075 V / 100 A = 0.00075 ohm, or 0.75 milliohm. This page performs that check directly and also reports the full-scale loss.
How do I verify a shunt with a measured current and measured drop?
Apply a known test current, measure the millivolt drop at the shunt terminals with Kelvin leads, and compare that measured drop against the expected drop from the nameplate resistance. The calculator reports the error percentage and a correction factor for meter scaling.
What does meter-to-shunt compatibility mean here?
A panel meter or transducer usually expects a specific full-scale millivolt input such as 50 mV or 75 mV. If the shunt rating does not match that input, the displayed current will be mis-scaled even if the shunt itself is healthy. The calculator shows the actual current that will reach meter full scale on the selected shunt.
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