tool4.dev

Electronics / LOCAL TOOL

Ohm's Law & Power Calculator

Solve voltage, current, resistance, and power from any two known values.

Runs locally — input is never uploaded
Known valuesFill any two; leave the rest blank

Only two fields are required.Type a plain base-unit value or include an unit such as mA, kΩ, or mW. Any extra values are checked against the solved circuit.

ResultReady when you are
V=IRP=VI=I2R=V2R

WHAT IT DOES

Solve the four resistive-circuit quantities from any two.

Supply any two of voltage, current, resistance, and power to solve the other two. If you enter extra measurements, the calculator checks them against the same ideal resistive model and flags disagreement beyond 0.5 percent.

Why use it?

Use it to check the relationship between steady-state voltage, current, resistance, and power in an ideal resistive circuit.

How to use this tool

  1. Enter any two known positive values, using engineering units where helpful, and leave unknown fields blank.
  2. Solve and review the other values. For example, 5 V across 1 kΩ gives 5 mA and 25 mW.
  3. If supplying extra measurements, review inconsistency errors instead of discarding them. Component ratings, transients, and temperature effects need a separate design check.

Details and limitations

  • Inputs accept common engineering prefixes such as mA, kΩ, MΩ, and mW while preserving the case-sensitive difference between milli and mega.
  • The result names the equations used instead of presenting an unexplained set of numbers.
  • The model uses positive steady-state magnitudes. It does not account for reactance, temperature coefficient, startup current, pulsed loading, or safe component derating.

WORKED EXAMPLES

Check current and power together

Start with the current and power fields empty, load these voltage and resistance values, and solve. This is an ideal positive-magnitude DC example, not a component-rating recommendation.

Voltage

5 V

Resistance

1 kΩ

Expected result

Current 5 mA and power 25 mW. Supplying an inconsistent extra current measurement should produce an error rather than silently choosing which measurement to trust.

COMMON QUESTIONS

Ohm's Law questions

Why does entering three values produce an inconsistency error?
The tool solves from a valid pair and compares every extra value with that solution. A difference over 0.5 percent indicates rounding, measurement variation, or a circuit that is not described by an ideal resistor.
Can this size a real resistor safely?
It calculates ideal steady-state dissipation. Choose a part using its datasheet, required derating, ambient temperature, transient or pulse energy, voltage rating, and applicable safety margin.