Calcscape

Ohm's Law Calculator

V = I × R, plus power P = V × I. DC sketch only. Click any i for detail.

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Circuit

Solve for
i
Mode

Enter the two known values; the third is calculated.
Volts
i
Volts

Used when solving for I or R. Ignored as an input when solving for V.
Amps
i
Amps

Used when solving for V or R.
Ohms
i
Ohms

Used when solving for V or I.

How to use this calculator

  1. Pick whether to solve for volts, amps, or ohms.
  2. Enter the other two values.
  3. Read the unknown plus watts.
  4. AC power factor and three-phase kVA are not on this page.

Results explained

Ohm’s law: V = I × R. Power P = V × I (also I²R or V²/R). This is DC or resistive-AC sketch math.

Quick reference: Ohm’s law

Keep units consistent (volts, amps, ohms, watts).

ItemDetail
VI × R
IV ÷ R
RV ÷ I
P (watts)V × I
12 V, 2 A, 6 Ω24 W

For feeder voltage drop over a run, use the voltage drop calculator.

How the estimate is built

V = I R; I = V / R; R = V / I; P = V I.

Example scenario

2 A through 6 Ω → 12 V and 24 W.

FAQ

AC motors?

Power factor and RMS vs peak are not modeled.

Watt’s law only?

P is shown alongside Ohm’s law, not as a separate mode.

Wire size from amps?

See the wire size calculator.