EleCalculator

Testing & Measurement calculator

Current Shunt Calculator

This current shunt calculator is a DC screening tool for three practical tasks: sizing a shunt from rated current and target millivolt drop, deriving an ammeter shunt from meter-movement data, and checking the voltage drop and power loss of a known shunt resistance. Example: a 10 A shunt with a 75 mV target drop needs 7.5 mΩ and dissipates 0.75 W at full current. The engine stays on the real formulas behind these jobs: R = V / I for millivolt shunts and Rs = (Im x Rm) / (I - Im) for classical ammeter range extension. It does not model AC skin effect, current transformers, Hall sensors, or detailed thermal certification.

Updated July 10, 2026

A 10 A shunt rated at 75 mV needs 7.5 mΩ and dissipates 0.75 W at full current.

Rshunt = Vshunt ÷ I | 75 mV ÷ 10 A = 7.5 mΩ

Choose the current-and-mV, ammeter-shunt, or known-resistance mode below to size or check a DC shunt

Calculator Inputs

Quick Presets

Choose whether you are sizing a shunt from its target millivolt drop, deriving an ammeter shunt from meter data, or checking an existing shunt resistance.

Use the full-scale DC current that will flow through the shunt.

Calculation Results

Enter values above to see calculation results

Field kit

Bench kit for shunt checks

Pair the calculated shunt value with measurement tools and low-resistance parts for a controlled bench setup.

Compare multimetersFor millivolt readingsOpens in a new tabFind shunt resistorsCheck wattage and toleranceOpens in a new tabAdd test leadsFor bench connectionsOpens in a new tab

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Calculation history

Example Calculations

10 A shunt with a 75 mV dropSize a DC shunt from rated current and target millivolt drop.InputsCalculation Mode: Shunt DesignMaximum Current: 10Shunt Voltage: 75

How to Use

How to use the current shunt calculator

Use this page when the job is to size or check a DC current shunt. The calculator keeps the scope narrow on real shunt-resistor work instead of pretending to be a full measurement-platform design suite.

1. Choose the mode that matches the data you already have

  • Resistance from Rated Current and mV Drop converts the current and desired shunt drop into the required milliohm value.
  • Ammeter Shunt from Meter Movement derives the external shunt needed to extend an analog meter or meter movement.
  • Known Resistance to mV Drop and Power checks the burden voltage and power loss of an existing shunt.

2. Enter only the inputs required for that mode

  • Rated Current (A) is the full-scale DC current through the shunt.
  • Target Shunt Voltage Drop (mV) is commonly 50, 60, 75, or 100 mV for catalog shunts.
  • Meter Full-Scale Current (mA) and Meter Internal Resistance (ohm) are used only for ammeter shunt calculations.
  • Known Shunt Resistance (mohm) is used only when checking an existing shunt.

3. Read the main outputs

  • Required Shunt Resistance is the milliohm value needed for the selected job.
  • Rated Shunt Drop or Voltage Drop at Rated Current shows the burden voltage your circuit will see.
  • Power Dissipation is the resistive loss in the shunt at rated current.
  • Range Multiplier shows the ratio between line current and meter-movement current in the ammeter-shunt mode.

4. Keep the practical limits in mind

  • This page assumes a resistive DC shunt with negligible lead resistance.
  • High-current work still needs Kelvin connections, terminal-torque control, and a real power-rating check.
  • If your burden voltage is above about 100 mV, confirm that the connected meter or controller accepts that drop.
  • For AC waveforms, isolated sensing, or transient-heavy duty, move to a current transformer, Hall sensor, or manufacturer-approved shunt assembly instead of relying on this screen alone.

5. After the current shunt result

Once the shunt resistance, millivolt drop, and watts are known, carry the result into the measurement record before selecting hardware or connecting an instrument.

  • Use the Shunt Resistor Power Burden Worksheet when the next step is recording burden voltage, shunt watts, meter input range, calibration status, and temperature-rise notes.
  • Use the Current Shunt Voltage Chart to document rated current, shunt resistance, mV output, meter range, lead arrangement, heat, and calibration follow-up.
  • Use the Shunt Calculator when you need to verify an existing shunt from its nameplate, measured mV drop, or meter-input match.
  • Use the Ohm's Law Calculator for quick V-I-R checks without shunt-specific outputs.
  • Use the Power Calculator when you only need a direct power check.
  • Use the Voltage Drop Calculator when conductor loss and line length matter along with the shunt burden.

Common Applications

Sizing 50, 75, or 100 mV DC shunts from rated current
Deriving external ammeter shunts from meter-movement current and resistance
Checking burden voltage before connecting a shunt to a meter, display, or controller
More applications. Open to review 2 additional use cases.
Estimating shunt heat loss before choosing a catalog power rating
Comparing a measured shunt resistance against common catalog drops at one current

Frequently Asked Questions

How do I calculate shunt resistance from current and millivolt drop?
Use R = V / I. A 75 mV shunt for 10 A is 0.075 V / 10 A = 0.0075 ohm, which is 7.5 milliohms. The calculator handles that conversion directly and also reports the corresponding power loss.
How does the ammeter shunt formula work?
For a classical meter movement, the shunt is sized so the meter and shunt share the same full-scale voltage. The calculator uses Rs = (Im x Rm) / (I - Im), where Im is the meter current, Rm is the meter resistance, and I is the desired full-scale line current.
What power rating should I choose for a current shunt?
Start with the calculated I^2R loss at rated current, then compare it with the actual continuous-duty rating of the shunt assembly. The calculator gives the electrical loss only; terminal temperature rise, enclosure heating, and manufacturer mounting rules still control the final selection.

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