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Voltage Drop Calculator

Enter your values below to get the result first, then scroll for the full explanation and guidance.

Step 1 • Add values

Use the calculator

Enter your values below to generate an instant result. You can update the inputs at any time to compare different scenarios.

Example: 5 A through 0.4 ohms of total path resistance gives 2 V drop.

Results refresh instantly as values change.

Voltage drop

2 VOhm's law: V = I × R

Voltage drop: 2 V (Ohm's law: V = I × R)

Multiply current in amperes by the known resistance in ohms. For a voltage-drop estimate, enter total path resistance.

Electrical values

Multiply current in amperes by the known resistance in ohms. For a voltage-drop estimate, enter total path resistance.

Result snapshot

A quick visual read of the values behind this result.

Current5 A
Resistance0.4 ohms

Recommended next checks

  • →Use measured or otherwise established resistance; this tool does not determine wire resistance.
Current
5 A
Resistance
0.4 ohms

Try different values to compare results.

Enter current and the known total resistance of the relevant path to estimate voltage drop. The calculator does not determine resistance from wire dimensions.

Inputs and units stated

Formula shown

Scope limits explained

Table of Contents

6

About Voltage Drop Calculator

Voltage Drop Calculator helps you work through the main numbers for this topic quickly with a simple input flow and an instant result.

Use the calculator result as a practical starting point, then review the explanation and assumptions on the page if you want more context.

Voltage drop formula

Voltage drop (V) = current (A) x total path resistance (ohms). Five amperes and 0.4 ohms give a 2 V drop.

Formula explained

Ohm's law

Estimate voltage drop from current and known total path resistance.

Formula

Voltage = current (A) x resistance (ohms)

How the result is built

1Enter the labelled values using the stated units.
2Apply Voltage = current (A) x resistance (ohms).
3Read the result alongside the page assumptions and scope limits.

Example

Example: 5 A through 0.4 ohms of total path resistance gives 2 V drop.

Assumptions

  • Known total path resistance includes the relevant circuit path.
  • This tool does not infer conductor resistance, temperature effects or regulatory compliance.

Source basis

  • OpenStax Physics, Ohm's law

FAQ

Common questions

No. Enter the established total path resistance; cable material, length and temperature are outside this tool.

Trust and notes

Assumptions and important notes

This calculator is designed to give a fast estimate using the method shown on the page. Results are most useful when your inputs are accurate and the tool matches your situation.

Use the result as guidance rather than a final diagnosis or professional decision. If the result could affect health, legal, financial, or compliance decisions, verify it with a qualified source where appropriate.

  • Known total path resistance includes the relevant circuit path.
  • This tool does not infer conductor resistance, temperature effects or regulatory compliance.

Method

Ohm's law

Last reviewed

October 12, 2026