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MaterialCalc — Romex Wire Footage & Cost Calculator

Estimate prepared 09/01/2026. Estimates only; verify against your plans before ordering.

Romex Wire Footage & Cost Calculator

Panel to the furthest device on the circuit, following the framing.

Outlets, switches and fixtures. Each needs a box and a wire tail.

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Tails in every box and the runs you measure wrong.

Result

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Wire estimates go wrong in two places: the runs are longer than the straight-line distance because cable follows the framing, and every box takes a tail that never carries current. Across a whole house those tails are hundreds of feet. This counts both and tells you how many 250 ft rolls to buy.

Assumptions used

These are the numbers behind the result. Where one of them is soft, the cost range widens rather than pretending to a precision the data does not have.

Wire tail left in each box
8 in

NEC 300.14 minimum free conductor — Published product data, checked 09/01/2026

Wire waste allowance
0.15

Covers the tail left in each box and the runs you measure wrong.

Standard electrical practice — Industry standard, varies by supplier, checked 09/01/2026

Prices verified 09/01/2026 (US national average, big-box retail shelf price and regional ready-mix quotes). Regional adjustment: Blended from RSMeans city cost index bands and BLS construction wage differentials.

The formula

Wire = (average run length × circuits) + (tail length × 2 × devices per circuit × circuits), plus a waste allowance. The NEC requires at least 6 in of free conductor at every box; 8 in is the practical working figure. Rolls = total feet ÷ 250, rounded up.

Worked examples

8 circuits at 45 ft, 6 devices each

Average run length: 45 Number of circuits: 8 Devices per circuit: 6 Wire size: 12-2 Waste: 15

About 490 ft including 64 ft of tails — two rolls. A typical single-story rough-in.

20 circuits at 60 ft for a whole house

Average run length: 60 Number of circuits: 20 Devices per circuit: 8 Wire size: 12-2 Waste: 15

Roughly 1,630 ft, or 7 rolls. Tails alone are over 200 ft — nearly a full roll of wire that never carries a load anywhere.

6 lighting circuits in 14/2

Average run length: 40 Number of circuits: 6 Devices per circuit: 5 Wire size: 14-2 Waste: 15

14/2 costs about a third less than 12/2 per foot. On lighting circuits that is a real saving, and it is easier to work with in a box.

Choosing materials

  • Measure the route, not the distance. Cable runs up a stud bay, across the top plate, along a joist and back down — routinely half again the straight-line figure between the panel and the device.
  • 12/2 is 20 amp wire and 14/2 is 15 amp. You can use 12 on a 15 amp circuit but never 14 on a 20 amp one, and mixing them on one circuit is a code violation that an inspector will find.
  • Buy full 250 ft rolls. Cut-to-length at the counter is priced well above the roll rate, and being 20 ft short at the end of a rough-in costs a trip.
  • Leave 8 in of conductor at every box, measured from the end of the sheathing. Six inches is the code minimum and it is a genuinely awkward amount to work with when you come back to make up the devices.
  • Staple within 12 in of every box and every 4-1/2 ft along the run. It is inspected, and a rough-in that has to be re-stapled is a wasted afternoon.

Common questions

How much Romex do I need for a house?

A typical 2,000 ft² house runs 1,500 to 2,500 ft across 20 to 30 circuits. Work it out per circuit — run length times circuits, plus tails at every box — rather than guessing from square footage, because layout matters more than area.

Should I use 12/2 or 14/2?

12/2 for 20 amp circuits — kitchen counters, bathrooms, laundry and general outlets in most modern work. 14/2 for 15 amp lighting circuits. Never put 14 gauge on a 20 amp breaker; the wire is the fuse in that arrangement.

How much wire should I leave in each box?

At least 6 in of free conductor measured from where the sheathing ends, which is the NEC minimum. Eight inches is far more comfortable to work with when you come back to install devices.

How long is a roll of Romex?

250 ft is the standard roll, with 100 ft and 1,000 ft also available. Buy full rolls: cut-to-length at the counter is priced substantially above the per-foot rate of a roll.

When do I need 12/3 instead of 12/2?

For three-way and four-way switching, for shared-neutral multiwire branch circuits, and for split-wired receptacles. It carries an extra hot conductor, and it costs about 50% more per foot.

How often does Romex need stapling?

Within 12 in of every box and at least every 4-1/2 ft along the run. Staples must be the type made for the cable and driven so they hold without crushing the sheathing.

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