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Wire resistance calculator

Compute the resistance of a wire from its length, cross-section and material.

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Need Resistance (Ω)? The Wire resistance calculator derives it from Length (m), Cross-section (mm²), Material in one step. For instance, with Length (m) = 10, Cross-section (mm²) = 2.5 and Material = Copper it returns Resistance (Ω) = 0.07.

How to use it

  1. Enter your values: Length (m), Cross-section (mm²), Material.
  2. Read the result instantly: Resistance (Ω).

Frequently asked questions

How does the Wire resistance calculator work?

It takes Length (m), Cross-section (mm²) and Material and derives Resistance (Ω) from them. The calculation is live as you type, so the result updates on every change.

Which values does the calculator ask for?

3 values: Length (m), Cross-section (mm²) and Material. Nothing else is required — no account, no file upload.

What does a typical calculation look like?

With Length (m) = 10, Cross-section (mm²) = 2.5 and Material = Copper, the calculator returns Resistance (Ω) = 0.07. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

How much does the result change with different inputs?

It moves a lot. Using Length (m) = 11, Cross-section (mm²) = 5 and Material = Aluminium instead, Resistance (Ω) goes from 0.07 to 0.062 — which is why it is worth testing a few scenarios rather than trusting a single figure.

Which “Material” option should I choose?

You can pick between « Copper », « Aluminium », « Gold » and « Silver ». Each one changes what the calculator works out, so switch and compare — the default is « Copper ».

What does it give for smaller values?

Scaled down to Length (m) = 9, Cross-section (mm²) = 1.3 and Material = Copper, Resistance (Ω) comes out at 0.121. The relationship is worth checking at both ends before you rely on a single result.

When would I actually use this?

Putting a number on a bill: what an appliance costs to run, whether a solar array covers the load, and how much heating a room actually needs.

What is the most common mistake?

Confusing power with energy. A kilowatt is a rate and a kilowatt-hour is a quantity; a 2 kW heater on for half an hour uses 1 kWh, and only the second figure appears on a bill.

What is the difference between the Wire resistance calculator and the Wire Gauge Calculator?

This one returns Resistance (Ω); the Wire Gauge Calculator returns Minimum cross-section. That is the whole difference — open the one whose figure you need.

Is there a tool for the next step?

Voltage drop calculator is the closest one after this: Estimate the voltage drop in a copper cable from its length, current and cross-section.

Further reading

All guides →
How-toWhat Wire Gauge Do I Need?Pick wire size from the load current, run length, and allowed voltage drop — the amps decide the minimum cross-section, distance forces you thicker.How-toHow Much Does a Space Heater Cost to Run?Multiply the heater's kilowatts by hours used and your price per kWh — a 1.5 kW heater for 5 hours a day adds up fast at typical tariffs.How-toHow Many Amps Does an Appliance Draw?Divide the appliance wattage by the supply voltage to get the current in amps — the number that decides breaker size, wire, and what can share a circuit.ExplainerHow Many Cables Fit in a Conduit? It Is a Code Question, Not a Geometry QuestionThe 40 % limit for three or more conductors is not about whether they physically fit. It is about heat and about pulling them in without stripping the insulation — and the moment you use that space, the code takes current away from every conductor in the pipe.ExplainerWhat Is Voltage Drop? Why Long Wires Lose VoltageVoltage drop is the voltage lost along a wire due to its resistance. Learn how length, gauge, and current affect it, and why it matters for your circuits.How-toHow to Estimate the Running Costs of a HomeAdd up energy, water, heating, and maintenance with simple rules of thumb so you know what a home really costs to run each month.