volts to ohms

Resistance is what a voltage pushes against: R = V/I. An LED running on 5 V at 20 mA needs a series resistor — and choosing it is exactly this conversion. The same calculation sizes the resistance of heating elements, sensor dividers, and every load that converts voltage into current.

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volts
amps
— ohms
— —

Authority: NIST SP 811 (SI usage guide) and the 1959 International Yard and Pound Agreement. The coefficient above is a defined value — it does not come from measurement and carries no uncertainty.

volts to ohms

The resistor question is the most common Ohm's law task in electronics: given a supply voltage and a desired current, what resistance limits the current to that value? For an LED, subtract the LED's forward voltage first (roughly 2 V for red, 3 V for white), then apply R = V/I to the remaining voltage. The result for 5 V minus 2 V at 20 mA is 150 Ω — the classic LED resistor. The same math runs heating elements, where resistance is fixed and current follows the voltage applied.

ohms = volts ÷ amps
R = V/I
Exact Ohm's law — the ratio of the voltage and current you provide.

Common volts to ohms Values

voltsampsohmsContext
5 V0.02 A250 ΩLED resistor at 5 V (minus 2 V forward = 150 Ω).
12 V0.02 A600 ΩLED resistor at 12 V.
120 V15 A8 ΩUS branch circuit load.
240 V10 A24 ΩDryer heating element.
3.3 V0.005 A660 ΩSensor pull-up at 3.3 V.

Engineering Context

Volts-to-ohms is one corner of the four-way Ohm's law family with volts to amps and amps to volts. The LED resistor angle connects to the electric hub's current pages, and the heating-element angle connects to the energy family — resistance at fixed voltage is how a heater's wattage is determined.

More: Ω to V · V to A · A to V · Electric Hub

Related Unit Converters

Ohms To Volts Volts To Amps Amps To Volts Electric Converters

Frequently Asked Questions

How do I convert volts to ohms?

Divide volts by amps: R = V/I. A 5 V circuit pushing 20 mA has an effective resistance of 250 Ω. If you know watts instead, R = V²/P.

How do I choose an LED resistor?

Subtract the LED's forward voltage (about 2 V for red, 3 V for white) from your supply, then divide by the desired current. For 5 V and 20 mA: (5 − 2) / 0.02 = 150 Ω.

Why is Ohm's law called a law?

Because it is exact for ohmic materials (resistors, wire, heating elements) at a fixed temperature: current through them is precisely proportional to voltage. That proportionality is the law, and R = V/I is its statement.