Introduction
Wire is one of those materials where the cost per foot hides the real budget: a long branch circuit, an upsized gauge for voltage drop, or a switch from copper to aluminum can each move the total by an order of magnitude. A realistic wire budget comes from three numbers — the per-foot price of the chosen gauge and insulation, the total circuit length including terminations, and the labor or tooling the wire demands.
The Wire Size Calculator gives you the first piece of the puzzle: the minimum gauge that satisfies ampacity and voltage drop for your load and run. This guide covers the rest — what wire costs, what drives the price, and how to budget a circuit or feeder without surprises.
What Drives Wire Cost
Four factors set the price of any conductor:
- Metal and gauge. Copper costs more than aluminum, and price climbs steeply with size — jumping from 12 to 10 AWG roughly doubles the copper per foot (6,530 → 10,380 circular mils), while a 4/0 feeder can cost many times a branch-circuit wire per foot.
- Insulation type. NM-B (Romex-style) sheathed cable, THHN/THWN-2 individual conductors, and UF-B direct-burial cable sit at different price points for the same gauge; outdoor and underground ratings cost more.
- Form. Cable (pre-assembled conductors in one jacket) vs. single conductors pulled through conduit — singles are cheaper per conductor-foot but require conduit and labor.
- Copper market price. Copper is a commodity; wire prices move with it. A quote from six months ago may be stale.
Because prices move with the copper market and vary by supplier and region, any per-foot figure should be verified with a current supplier quote — the estimating method below is what stays constant. For the conductor differences behind the price, see the material guide.
The Cost Formula
Wire material cost
Material cost = (one-way length × 2 + termination allowance) × price per foot × number of conductors
A circuit needs out-and-back conductors (plus ground), so double the route length first. Add a termination allowance — extra length at each box and the panel for making connections. Electricians commonly allow 15–30 cm (6–12 in) of free conductor per device box and more at the panel.
Conduit and fittings
Individual THHN conductors need conduit: conduit cost = run length × price per foot + fittings. Conduit itself can rival the wire cost on long runs, and fittings (couplings, connectors, LB bodies) add up fast at each bend and transition.
Labor share
Wire pulling is labor: long runs, many bends, and large gauges all slow the pull. Oversized wire (chosen for voltage drop) is stiffer and heavier — the pro-tips guide covers techniques that keep pulling costs down.
Worked Example: Budgeting a Workshop Circuit
Recall the workshop circuit from the complete guide: 20A, 120V, 15 m (49.2 ft) one-way, requiring 10 AWG copper for voltage drop. Budget it:
Step 1 — Conductor length. 15 m one-way × 2 = 30 m (98.4 ft) of current-carrying conductor, plus ground. Termination allowance: 6 boxes × 0.25 m = 1.5 m per conductor ≈ 2 m (6.5 ft) extra each.
Step 2 — Totals per conductor. 30 + 2 = 32 m (104.9 ft). Three conductors (hot, neutral, ground) → 96 m (314.7 ft) of 10 AWG total.
Step 3 — Material. 96 m × price per meter = your wire cost. Cross-check in imperial: 104.9 ft × 3 conductors = 314.7 ft total — identical length, different units.
Step 4 — Sanity check. Compare the cost against the alternative: if the run were half as long, 12 AWG would satisfy voltage drop — roughly half the copper per foot. Long runs don’t just buy more feet; they buy thicker feet.
Practical takeaway: on long circuits, shortening the route is a cost tool. Moving a subpanel 10 m closer to the load can drop a gauge size and cut copper weight dramatically. For a full estimation workflow, see the estimating guide.
Copper vs Aluminum on Cost
For branch circuits (14–10 AWG), copper is the practical default and the price differences between gauges are modest. The copper/aluminum cost decision matters on feeders and services:
| Factor | Copper feeder | Aluminum feeder |
|---|---|---|
| Material cost per amp | Higher | Lower — typically the reason aluminum is chosen |
| Gauge for same ampacity | Smaller (e.g., 2 AWG) | One size larger (e.g., 1/0) |
| Terminations | Standard | Must be aluminum-rated, properly torqued |
| Weight | Heavier | Lighter — easier long pulls |
Aluminum’s savings show up at 6 AWG and larger; below that, copper’s small price premium buys simpler terminations. Note that local code and your AHJ may restrict aluminum in some applications — confirm before budgeting around it, per the code-compliance guide.
Mistakes That Inflate Wire Budgets
- Forgetting the return conductor. Budgeting one-way length halves the wire cost — every circuit is out and back.
- Omitting termination allowance. Boxes and panels consume real wire; a dozen boxes at 25 cm each is 3 m per conductor.
- Ignoring the ground. Equipment grounding conductors are required; their gauge follows its own table and must be bought too.
- Sizing from stale prices. Copper moves — re-quote before committing a large feeder budget.
- Counting only the wire. Conduit, fittings, breakers, and devices often exceed the conductor cost on a circuit.
- Oversizing “just to be safe” without math. Two gauges up on a long run can double material cost; size to the actual voltage-drop calculation.
More estimating errors are catalogued in the common mistakes guide.
Related Guides
- Complete Guide — ampacity, voltage drop, and the sizing workflow.
- Estimating Guide — the full material takeoff for a circuit.
- Wire Material Guide — copper vs aluminum and insulation types.
- Formula Explained — the voltage-drop math step by step.
- DIY vs Pro — what drives the labor share of the bill.
Frequently Asked Questions
How do I estimate wire cost for a circuit?
Double the one-way run length, add termination allowances at each box and the panel, multiply by the per-foot price and the number of conductors, then add conduit, fittings, breakers, and devices.
Is aluminum wire cheaper than copper?
Yes, per amp of capacity — which is why it’s common for feeders and services at 6 AWG and larger. For small branch circuits the savings are minor and copper’s simpler terminations usually win.
Why does a longer run cost more than just extra feet?
Because long runs force larger gauges for voltage drop — you buy more feet of thicker wire. Shortening the route can drop a gauge size entirely.
Should I include conduit in the wire budget?
Yes, whenever individual conductors (THHN) are used instead of sheathed cable. Conduit plus fittings can rival the conductor cost on long runs.
How much extra wire should I allow at each box?
A common rule is 15–30 cm (6–12 in) of free conductor per device box, more at the panel. Sum it across all boxes — it adds up on circuits with many devices.
Do copper prices really change that much?
Copper is a traded commodity, so wire prices fluctuate over months. For large feeder purchases, always get a current quote rather than budgeting from an old receipt.
Get Your Number
Budget wire by doubling the run, adding termination allowances, and pricing the gauge the math actually requires — not a guess. The Wire Size Calculator gives you the minimum gauge from ampacity and voltage drop; multiply out the lengths and current per-foot prices for your total, and get a licensed electrician to review the plan before purchasing.
Disclaimer: Calculator results are planning estimates based on the values you enter. Material prices vary by supplier, region, and commodity markets — verify all pricing with current quotes. Electrical work is regulated in most jurisdictions; consult a licensed electrician and your local authority having jurisdiction (AHJ) before installing or altering wiring.
