Science calculator

Ohm's law.

For an ohmic conductor the voltage across it equals current times resistance, V = I R. Type the two values you know and leave the one you want blank — it appears on the display, with the electrical power P = V I shown alongside. GCSE and A-level; assumptions below.

Voltage V

Current I

Resistance R

Voltage V

—

Electrical power P = V I: —

Display precision

V = I R

I = \frac{V}{R}

R = \frac{V}{I}

P = V I

V voltage (V) · I current (A) · R resistance (Ω) · P power (W)

Assumptions

An ohmic conductor: resistance is constant, so current is proportional to voltage.
Constant temperature — a filament lamp or thermistor is not ohmic and won't follow this line.
Steady (DC) values; R is the total resistance across which V is measured.
SI units: volts, amps, ohms; power in watts.

How it works

Ohm's law ties the three quantities together: for a fixed resistance, more voltage drives more current. Rearranged, it finds any one from the other two — leave that box blank. The power dissipated is P = V I (equivalently I²R or V²/R), shown for every result.

Results use up to three significant figures by default (adjustable above), without padding the display with trailing zeroes. Remember it only holds for ohmic components at constant temperature.

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