The wire weight calculator above answers a question that comes up constantly and has no convenient chart when you need one: how much does this run of conductor actually weigh? Copper is bought by the kilogram, scrapped by the kilogram, shipped by the kilogram and carried up ladders by people, so the mass of a spool matters for costing, for freight, for structural loading on a cable tray and for deciding whether the reel goes on a trolley or a truck.
The arithmetic is simple and the traps are all in the inputs, which is why the tool shows you every intermediate value. Arb Digital publishes two adjacent wire pages that answer different questions from the same geometry, and the boundary is clean: the wire size calculator picks a conductor size from a load current, a run length and a voltage drop limit, using ampacity and drop as its two tests, and it computes nothing physical about the metal. The wire resistance calculator turns the same geometry into ohms. This page turns it into kilograms. Size first, then resistance, then weight — three different questions about one conductor.
What This Wire Weight Calculator Does
It computes the conductor's cross-sectional area from either an AWG gauge number or a measured diameter, multiplies by length and by the material's density, and multiplies again by the number of conductors. It reports the total weight in kilograms and pounds, the mass per metre, the weight per thousand feet in pounds — the form North American cable tables use — and the cross-sectional area in square millimetres, which is the form the rest of the world specifies cable in.
It also compares your material against the same geometry in aluminium, because that swap is one of the standard levers in a large installation and the weight difference is dramatic. If you enter a price per kilogram, it costs the run out.
How to Use It
- Choose how the wire is specified. AWG for North American wire, measured diameter for metric cable, imported reels, magnet wire on an unmarked bobbin, or anything you have callipers on.
- Enter the gauge or the diameter. If you are measuring, measure the bare conductor, not the outside of the insulation, and measure in two places at right angles in case the wire has been flattened.
- Enter the length and the conductor count. A two-wire circuit of 50 m one-way length is 100 m of conductor, and forgetting the return leg is the most common error on this page.
- Pick the material. Copper and aluminium differ in density by a factor of about 3.3, which is the whole reason large feeders are so often aluminium.
- Add a price if you are costing. Enter your own quoted rate per kilogram; the tool assumes nothing about metal prices.
The Formula, and Where AWG Diameters Come From
The mass of a solid cylinder is m = ρ × (π/4) d² × L, with ρ the density, d the conductor diameter and L the length. Everything on this page is that expression, multiplied by the number of conductors.
The interesting part is where d comes from when you give a gauge number. American Wire Gauge is a geometric progression, defined so that 36 AWG is 0.005 inches and 0000 AWG is 0.46 inches, with 39 steps between them. That gives a ratio of 921/39 between adjacent sizes, and the diameter of any gauge n as:
d = 0.005 in × 92(36 − n)/39, or in millimetres, d = 0.127 mm × 92(36 − n)/39.
Two consequences fall straight out of that geometry and are worth knowing without a table. Six gauge numbers is almost exactly a factor of two in diameter, and therefore a factor of four in area and weight. Three gauge numbers is almost exactly a factor of two in area. That is why an electrician can estimate in their head that going from 14 AWG to 8 AWG roughly quadruples the copper.
Work the default through. For 12 AWG, (36 − 12)/39 = 0.615385, and 92 raised to that power is 16.163, so d = 0.127 × 16.163 = 2.0525 mm. The area is (π/4)(2.0525 mm)² = 3.3088 mm², which agrees with the 3.31 mm² in the standard tables. At the annealed copper density of 8890 kg/m³, that is 0.029415 kg per metre, or 29.4 grams per metre, which is exactly the figure published for bare 12 AWG copper. A hundred metres therefore weighs 2.942 kg. The material properties that make copper and aluminium behave differently here are tabulated in OpenStax's chapter on resistivity and resistance.
Stranded Wire Weighs More Than Its Nominal Size
This is the single biggest source of error in a real estimate. A stranded conductor of a given AWG size has the same total copper cross-section as the solid wire of that size, by definition — but the strands are laid up in a helix, so each strand is longer than the cable it is inside. The lay length determines how much longer, and for ordinary building wire the increase is around one to three per cent, rising for finer, more flexible constructions with tighter lay.
That means a hundred metres of stranded 12 AWG contains rather more than a hundred metres of copper, and weighs correspondingly more than this page reports. For a costing exercise on a large order that percentage is real money. For very flexible cable with hundreds of fine strands and multiple layers of lay, the effect is larger still. The tool computes the solid-equivalent weight, which is the correct baseline; add the lay allowance from your cable's own data sheet on top.
The overall diameter of a stranded conductor is also larger than the solid one of the same size, because of the gaps between strands. So if you measure a stranded conductor with callipers and enter that diameter, you will overestimate the metal. For stranded wire, enter the AWG size rather than the measured outside diameter.
Copper Against Aluminium, and What the Swap Really Costs
Aluminium's density is about 2705 kg/m³ against copper's 8890, so a conductor of identical dimensions weighs about 30 per cent of the copper one. That is the number the bar chart shows, and on its own it overstates the advantage, because aluminium is also a poorer conductor: its resistivity is roughly 1.6 times copper's, so matching the electrical performance needs a larger cross-section, conventionally about two AWG sizes up.
Do that comparison properly and aluminium still wins on weight by a wide margin — roughly half the mass of copper for the same current-carrying capability — which is why overhead transmission lines and large service entrance feeders are aluminium almost everywhere. What it costs is diameter, and therefore conduit fill, bending radius, termination size and the need for connectors rated for aluminium. Working out the electrical side of that trade is what the wire resistance calculator and the voltage drop calculator are for, and the wire size calculator handles the sizing decision itself.
What This Weight Does and Does Not Include
Everything here is bare metal. A finished cable adds insulation, a filler, a jacket, sometimes a screen and sometimes steel wire armour, and for a small conductor the non-metallic content can easily exceed the weight of the copper inside it. On a large power cable the metal dominates and the addition is proportionally smaller, but armour is heavy and changes that again. If you are working out whether a cable tray or a hanger can take a run, get the finished cable weight from the manufacturer; do not use this figure.
What this figure is right for is metal content: costing a copper purchase, valuing a scrap lot, estimating what a bare overhead conductor weighs per span, or checking whether a reel of magnet wire has been part-used. It is also the right basis for a transformer or motor winding calculation, where the conductor is what you are buying and the enamel is a few per cent. To move the result between units, the weight converter and the length converter cover the usual conversions, and the density converter handles a data sheet quoting density in some other form.
Arb Digital builds free tools like this one because genuinely useful pages earn attention. If you want calculators, tools or technical content built for your own audience, we can help.
Browse All Free Tools Talk to Arb DigitalCommon Mistakes to Avoid
- Counting only the one-way length — a circuit needs a return conductor, so a 50 metre run is 100 metres of wire before you count any earth.
- Measuring over the insulation — the weight depends on the metal diameter, and a millimetre of jacket on a small conductor more than doubles the apparent area.
- Entering a stranded conductor's measured outside diameter — the gaps between strands make it larger than the solid equivalent, so enter the AWG size instead.
- Ignoring the lay allowance on stranded cable — helically laid strands are longer than the cable, adding roughly one to three per cent of metal for ordinary constructions and more for very flexible ones.
- Using this as a cable weight for structural loading — insulation, fillers, jacket and armour are not included, and for small conductors they can outweigh the copper.
Related Free Tools From Arb Digital
To choose a size in the first place, use the wire size calculator, which tests a conductor against both ampacity and voltage drop. The wire resistance calculator turns the same geometry into ohms, the voltage drop calculator shows what that resistance does to the voltage at the load, and the Ohm's law calculator covers the arithmetic underneath both. For the material side, the density calculator handles mass and volume generally and the weight converter, length converter and volume converter reconcile units between data sheets. Everything Arb Digital publishes is indexed on the free online tools hub. For the wider electrical context in which conductor sizing sits, OpenStax's chapter on household wiring and electrical safety is a good grounding, and the circuit theory is developed in MIT OpenCourseWare's 6.002 Circuits and Electronics.
Frequently Asked Questions
About 2.94 kilograms as bare solid conductor. The gauge formula gives a diameter of 2.0525 millimetres, so the area is 3.3088 square millimetres, and at the annealed copper density of 8890 kilograms per cubic metre that is 29.4 grams per metre. Stranded wire of the same size weighs a little more because the strands are laid helically and are therefore longer than the cable containing them.
American Wire Gauge is a geometric series fixed by two endpoints: 36 AWG is 0.005 inches and 0000 AWG is 0.46 inches, with 39 steps between them. Each step is therefore a ratio of 92 to the power one thirty-ninth. That is why six gauge numbers is almost exactly a factor of two in diameter and four in area, and three gauge numbers is almost exactly a factor of two in area.
No, it weighs slightly more. The copper cross-section is the same by definition, but the strands are laid in a helix, so each strand runs a longer path than the cable it is inside. For ordinary building wire the lay allowance adds roughly one to three per cent, and for very flexible cable with many fine strands it is larger. This tool computes the solid-equivalent weight, and the lay allowance goes on top of it.
For identical dimensions, an aluminium conductor weighs about 30 per cent of the copper one, because the densities are roughly 2705 against 8890 kilograms per cubic metre. That comparison flatters aluminium, though, because its resistivity is about 1.6 times copper's, so matching the electrical performance takes a larger cross-section. Compared at equal current-carrying capability, aluminium is still roughly half the weight.
No. Everything here is bare conductor. A finished cable adds insulation, fillers, a jacket and sometimes a screen or steel wire armour, and on a small conductor the non-metallic content can weigh more than the copper inside it. For structural loading on a tray or a hanger, use the finished cable weight from the manufacturer's data rather than this figure.
Because a circuit is almost never one wire. A two-wire run of 50 metres one-way length contains 100 metres of conductor, and adding a protective earth makes it 150. Entering the conductor count keeps the length field meaning the physical run rather than the total metal, which is how cable is usually measured and quoted.
Use 8890 kilograms per cubic metre for annealed copper if you want your answer to agree with the standard conductor tables, since that is the value they are built on. Pure copper at 20 degrees Celsius is closer to 8960, and the difference is under one per cent. Alloys, plated wire and composite conductors such as aluminium-conductor steel-reinforced need their own figures, and no single density describes a composite.
Yes, for the copper content, which is usually what you want when you are working out how much wire a winding takes or checking how much is left on a bobbin. Enamel insulation on magnet wire is thin and adds only a few per cent to the weight, but it does add to the outside diameter, so enter the bare conductor diameter from the wire's specification rather than a calliper reading over the enamel.
This calculates bare solid-conductor weight from the dimensions and density you supply. It does not include insulation, stranding lay allowance or armour, and it is not a substitute for the manufacturer's data for a specific cable.
