Electrical Fundamentals
Shunt Resistor Calculator
Size an ideal current-measurement shunt. The default values illustrate the workflow; replace them with measurements or ratings from one documented condition.
Calculate Shunt resistance
Replace the examples with values from the same case.
How the result is calculated
Start with the equation Rshunt = Vshunt ÷ I. Its variables correspond to Full-scale shunt voltage and Full-scale current.
For the example shown, shunt resistance equals 0.000750 Ω. Treat that value as a demonstration, not a recommendation.
Size an ideal current-measurement shunt. A separate conductor resistance result is available from Conductor Resistance Calculator.
Values this page needs
Keep source conditions with each voltage, current, resistance, or charge value. Do not combine a worst-case value with unrelated nominal data.
At least one field has a positive lower bound because it appears in a denominator. Convert units once, retain the original reading, and verify the converted magnitude.
- Full-scale shunt voltage
- Default example: 0.075 V. Enter full-scale shunt voltage in V.
- Full-scale current
- Default example: 100 A. Enter full-scale current in A.
Checks that catch bad inputs
Values recorded at different operating points should not share one case.
Check the input source before adding a safety or correction factor.
What the formula leaves out
Select a real shunt with adequate power rating and a suitable Kelvin connection.
A complete model can also include instrument loading, transient behavior, and component tolerance. Do not hide omitted behavior inside an unexplained correction factor.
Use readings taken at the same circuit state and reference node.
Sensitivity check
Change Full-scale shunt voltage from 0.075 V to 0.09 V and leave all other entries untouched. The displayed value changes from 0.000750 Ω to 0.000900 Ω.
Keep both cases when the changed input represents genuine uncertainty.
Using this result in a larger analysis
Check the source of full-scale shunt voltage before calculating. A credible result requires every field to describe the same physical condition and unit basis.
Use shunt resistance alongside the expected circuit operating point. Preserve the unrounded number until all dependent calculations and comparisons are complete.
If uncertainty remains, calculate labeled low and high cases. Include lead and contact resistance, source impedance, and temperature drift when those effects can change the decision.
Questions from practical use
Does the answer include a design margin?
No. Compare the value with bench measurements and component ratings and apply relevant equipment and installation requirements.
Why does Shunt resistance show several decimals?
Retain the raw result for comparison and create a separately rounded reporting value if needed.
Why is zero rejected for one of the fields?
Use a measured positive value for Full-scale current; zero cannot stand in for missing data.