What formula does this calculator use?

It uses R = 2E / (I²·t), derived from the energy formula E = ½·I²·R·t. This applies to resistive elements where energy dissipation is proportional to I²·R·t.

When is this formula valid?

It is valid for purely resistive (ohmic) loads with constant current over the time period t. For AC circuits or non-constant current, additional analysis is required.

Why does the formula have a factor of 2?

The factor of 2 comes from rearranging E = ½·I²·R·t. Solving for R gives R = 2E / (I²·t).

What units must I use?

Energy in joules (J), current in amperes (A), and time in seconds (s). The result is in ohms (Ω). Convert milliamps to amps (divide by 1000) and milliseconds to seconds (divide by 1000) before entering values.

Can I enter zero for current or time?

No. Both current and time appear in the denominator, so zero produces a division-by-zero error. Enter positive non-zero values only.

How do I convert kilowatt-hours to joules?

Multiply kWh by 3,600,000 to get joules (1 kWh = 3.6 MJ).

Joules to Ohms Calculator

Name: Joules to Ohms Calculator
Availability: InStock
Author: Nham Vu

Calculate electrical resistance in ohms from energy (joules), current (amperes), and time (seconds) using R = 2E / (I²·t).

Enter Values

Energy (J) *

Joules of energy dissipated or stored

Current (A) *

Steady-state current through the element

Time (s) *

Duration in seconds

Formula

R = 2E / (I² × t)

Enter energy, current, and time, then click Calculate.

Resistance

0 Ω

Calculation

Parameter	Value

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Summary

Calculate electrical resistance in ohms from energy (joules), current (amperes), and time (seconds) using R = 2E / (I²·t).

How it works

Enter the energy value in joules (J).
Enter the current value in amperes (A).
Enter the time duration in seconds (s).
Click Calculate to apply R = 2E / (I²·t).
The result shows resistance in ohms along with derived voltage and power values.

Use cases

Determine the resistance of a heating element from its energy consumption, current, and run time.
Size a discharge resistor for a capacitor bank given energy, current rating, and discharge time.
Verify resistance of a circuit component using measured joule output and current.
Calculate motor winding resistance from thermal energy dissipation data.
Check wire resistance when energy loss, current, and duration are known.
Validate resistor values in pulse-power applications from energy and current specs.

Frequently Asked Questions

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Last updated: 2026-05-23 · Reviewed by Nham Vu