Guide · Footage
Working out footage from a reel weight
Weighing a reel is faster than unrolling it and usually close enough. The method has limits, and knowing them is what keeps an estimate from turning into an argument on the dock.
Request a quote
Tell the desk what you have in Estimating footage by weight
Send the basics and a buyer reviews the lot, usually the same working day.
- Reviewed by a buyer, not a scale
- Reels, pallets, partials or a full truckload
- Anywhere in Ohio, one desk
- 01Send the wire type, quantity and pickup city.
- 02A buyer reviews the lot and replies with a basis.
- 03Freight and release are agreed, then the load is booked.
Lot details
Everything helps, but the wire type, the quantity and the pickup city are enough to start.
The arithmetic of a partial reel
Two weighings and one constant get you most of the way. Weigh the reel gross, subtract the weight of the empty drum printed on a wooden flange or stamped into a steel one, and you have net cable weight. Divide that by the weight of one foot of the construction. For copper, a thousand circular mils comes to roughly 3.03 pounds per thousand feet, so 500 kcmil copper conductor runs near 1.5 pounds per foot before any insulation is added.
Aluminum is the second constant. At the same circular mil area it weighs about thirty percent of copper, close to 0.92 pounds per thousand feet per thousand circular mils. Add insulation and jacket for the smaller sizes, then divide, and you have an estimate with a defensible basis.
Why the answer is only an estimate
The method assumes the drum is the drum in the table, the tag is honest, and the cable is dry. None of those is a safe assumption in a laydown yard. Wood takes on water over a season and a soaked oak reel can weigh substantially more than its stamped tare. Steel rusts, and a reel that stood in a puddle carries water inside the wrap and between the strands.
Construction also varies more than a single constant suggests. Insulation wall, tape, fillers, interstitial compound, bedding and armor all add weight that has nothing to do with conductor length. On a 750 kcmil feeder the conductor dominates and the error is small. On a small control cable the jacket can be a third of the total, which is why the same arithmetic that works on feeders misleads on control.
Where the method is reliable
Weight works well on large single-conductor copper: 4/0 and above, bare or thinly jacketed, on a reel whose tare is legible. Bare copper is the simplest case because there is nothing on the cable but copper. A 4/0 bare conductor is close to 0.64 pounds per foot, so a net cable weight of 640 pounds is roughly a thousand feet.
Aluminum is workable if you respect the drum. Aluminum cable is light, so the tare becomes a large share of the gross; on a short reel of 350 kcmil aluminum the steel may weigh as much as the cable. Weigh an empty reel of the same pattern if one is available, and never use a tare from a different reel design.
When to measure instead
Measure when money depends on the answer. A partial reel under a few hundred feet is cheaper to measure than to argue about later. Lay the cable straight and run a measuring wheel along it, or pull it over a counter with a meter. Do not drag it across concrete to do it, because the jacket will not forgive that.
Measure as well when tagged footage and weight disagree by more than a few percent, when a reel has clearly been re-wound, and when two lengths have been joined onto one drum. A re-wound reel is an estimate regardless of what the label says, and saying so protects both sides.
What to send with the numbers
Send the gross weight, the tare if it is legible, the construction and size, and the tagged footage. Say which figure came off a scale and which came off a label. If you measured, say what you measured with.
A buyer will usually accept an estimate that is labelled as one. What gets discounted is an estimate presented as a measurement, because the correction then happens on the buyer's scale rather than on your manifest.
Related pages
Adjacent cities, wire families and regional briefs.
Other seller guides
All guides- Reading a reel tagWhat the tag carries and what a missing one costs
- Copper versus aluminium valueTwo metals, two sets of facts
- Preparing a surplus manifestThe line items a buyer can actually price
- Photographing a reelSix photographs that answer most questions
- Medium voltage cable safetyIsolation, grounding and handling before removal
- Storing cable to protect insulationUV, water, ozone and reel orientation
Questions sellers ask
Can I estimate footage without the empty reel weight?
You can bracket it. Weigh the gross, then weigh an empty reel of the same size and material if the yard has one, and use that as the tare. If nothing comparable exists, say so and treat the figure as a range rather than a number, because an unknown tare on a steel drum can move the answer by hundreds of feet.
Does insulation weight matter on 500 kcmil?
Very little. On a large feeder the copper or aluminum dominates so completely that a jacket thickness difference moves the estimate by a percent or two. On 10 AWG and smaller the jacket, fillers and shield are a significant share of the weight, and the estimate should be given as a range.
Why does the same size in aluminum weigh less than a third?
Aluminum is about thirty percent of copper by weight at the same circular mil area, but an aluminum cable is usually built one size larger to carry the same current, so the conductor area goes up while the weight still falls. Compare weight per foot at the size actually printed on the jacket, not at the size it replaces.
Request a quote
Tell the desk what you have in Estimating footage by weight
Send the basics and a buyer reviews the lot, usually the same working day.
- Reviewed by a buyer, not a scale
- Reels, pallets, partials or a full truckload
- Anywhere in Ohio, one desk
- 01Send the wire type, quantity and pickup city.
- 02A buyer reviews the lot and replies with a basis.
- 03Freight and release are agreed, then the load is booked.
Second look at the lot
Everything helps, but the wire type, the quantity and the pickup city are enough to start.