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Ohms Law Calculator

Ohms Law Calculator is part of Toolspire and is ready as soon as this page loads. 2 amps through 5 ohms is 10 volts, and the power is 20 watts. This is the DC textbook equation. It is not a guide to household wiring.

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What you can do here

One unknown

The empty box is solved. Three filled boxes are not checked against each other, because you did not say which number is wrong.

Watts beside the answer

Once two of V, I and R are known, power is fixed too, and it is written in the detail.

DC and ideal

There is no AC impedance, no temperature rise, and no wire size. Those are not this equation.

The sequence

How to use the Ohms Law Calculator

  1. 1

    Clear the quantity the problem asks for

    If the question asks for voltage, leave voltage empty and type current and resistance.

  2. 2

    Use volts, amps and ohms

    Milliamps must be converted. 200 mA is 0.2 A. The page will not divide by 1000 for you.

  3. 3

    Read watts only as V times I

    The detail is that product. It is not a rating for a cable or a fuse.

Worth knowing

  • Ohms Law Calculator on Toolspire: V = I × R. 2 amps and 5 ohms give 10 volts.
  • I = V ÷ R and R = V ÷ I. 10 volts across 5 ohms is 2 amps. 10 volts at 2 amps is 5 ohms.
  • Power in the detail is P = V × I, in watts. For 10 V and 2 A that is 20 W.
  • Leave exactly one box empty. Zero resistance cannot give a current, and zero current cannot give a resistance.

The equation and nothing past it

Ohm’s law here is the DC relationship between voltage, current and resistance for an ideal resistor. Power is the product of voltage and current once those are known. The page stops there. It does not choose a wire, a fuse or a supply, and it must not be used as a reason to open a wall, a panel or a live circuit. Alternating current, reactance and a hot filament all leave this model.

FAQ

Questions about Ohms Law Calculator

Where does Ohms Law Calculator run?

Ohms Law Calculator runs in this tab on Toolspire. What you type or drop in is not sent to us and is not stored on a server.

What voltage is 2 amps through 5 ohms?

10 volts. Power is 20 watts, from 10 × 2.

What current is 10 volts across 5 ohms?

2 amps. Leave the current box empty.

Why is a zero resistance rejected when solving for current?

Current would be voltage divided by zero. The page returns no result instead of infinity.

Can I use this for house wiring?

No. It is a classroom DC calculation. It is not a wiring guide.

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