Ohm's Law: Find Current

I = V / R

Calculate current from voltage and resistance using Ohm's Law. I = V/R.

Calculate

Voltage V (V)

Resistance R (Ω)

Enter values above to calculate

How it calculates

I = V / R

V in volts, R in ohms

Result in amperes

Formula

I = V / R

Variable Table

Symbol	Quantity	SI Unit
I	Current	A
V	Voltage	V
R	Resistance	Ω
P	Power = IV	W

→ Ohm's Law article

How to Use This Calculator

This ohm's law: find current is built for quick physics checks and worked-problem review. Enter values in the units shown beside each input, then compare the result with the formula and variable table before using it in a longer solution. The calculator does the arithmetic, but the physics still depends on choosing a model that matches the situation.

Start by identifying the system, the known quantities, and the quantity you want to find. If a value is given in a non-SI unit, convert it before substitution. A correct numerical answer with mixed units can still be physically wrong, especially when squared units, inverse seconds, charges, temperatures, or distances are involved.

Assumptions and Limits

The formula I = V / R is a model, not a universal description of every possible case. It assumes the quantities in the variable table are the relevant quantities for the problem and that hidden effects are either negligible or already included in the inputs. If friction, drag, relativistic speeds, changing fields, non-constant temperature, or geometry-specific effects matter, check whether a more complete model is needed.

Use the result as a magnitude and units check. Ask whether the answer has the right sign, whether it grows or shrinks when an input changes, and whether the limiting cases make sense. Setting an input to zero, doubling a quantity, or using a very large value is often enough to catch a formula choice or unit mistake before it reaches a final answer.

Worked Example

A 12 V battery across a 6 Ω resistor. Find current.

Step 1: I = V / R

Step 2: I = 12 / 6

Answer: I = 2 A

Common Mistakes

I = V/R gives conventional current in direction of positive charge flow
Zero resistance is a short circuit (infinite current) — not physically achievable
Series: I same everywhere; Parallel: I splits proportionally

Ohm's Law Find Resistance Electromagnetism

Frequently Asked Questions

What is conventional current direction?

From + to − terminal (opposite to electron flow). In circuit analysis, both conventions are used — specify which you mean.

What is a short circuit?

When R → 0, I → ∞. In practice, wire resistance limits current, but short circuits can cause fires or blown fuses.