Free roof and gutter heat cable calculator: the cable length to order
Get the heat cable length for a roof edge, its gutter and its downspouts in seconds, free and without an account. One row per run: the length of roof edge, the heated gutter, how many heated downspouts and their length. Pick the maker and the roof overhang to fill the figures it prints, or type your cable's: the calculation gives the cable on the roof, in the gutter and in the downspouts, and the length to order, run by run. In imperial or metric.
Heat cables: what the makers print (reference)
Figures read in the makers' installation manuals. Each has its own rule: your cable's has the last word.
| Cable per foot of roof edge, by overhang | Gutter and downspouts | |
|---|---|---|
| Raychem IceStop | No overhang 2.5; 12 in 3.2; 24 in 4.2; 36 in 5.2; plus twice the gutter depth | Gutter up to 6 in wide: 1 pass, 6 to 12 in: 2 passes 6 in apart; downspout: 1 pass with its end looped back up at least 12 in, or 2 for high flow or below -10 °F |
| WarmlyYours | No overhang 2.5; 12 in 3.1; 24 in 4.2; 36 in 5.2 | 1 ft of cable per foot of gutter and of downspout, twice for a downspout in the middle of a run; 1 ft per power connection |
| Warmup WRGH | Up to 12 in 4.0; 24 in 5.3; 36 in 6.8; 72 in 11.2, gutter included (3.0 to 10.2 without a gutter) | Downspouts: twice their length; fixed-length kits from 30 to 240 ft, never cut |
Sources: Raychem IceStop manual; Raychem IceStop design guide; WarmlyYours roof and gutter manual; Warmup WRGH manual
How it is calculated
For each run: cable = roof edge x edge multiplier + heated gutter x passes in the gutter + heated downspouts x (length of each downspout x passes + added per downspout) + added per cable. The multiplier is the cable per foot of edge for the zig-zag on the roof, by overhang, from the maker's table. The runs add up. The same formulas as the gutter survey template; a number left empty counts 0, as in the app. Length only: the circuit, the breaker and the ground-fault protection are an electrician's work, per the maker's instructions.
Example: the back run, 12 in overhang
From our template page's demo: 61 ft of roof edge with 61 ft of heated gutter and 2 downspouts of 11 ft, a WarmlyYours cable at 3.1 for a 12 in overhang, 1 pass in the gutter and 1 down each downspout, and 1 ft for the power connection. That makes 189.1 ft on the roof, 61 ft in the gutter, 22 ft in the downspouts and 1 ft for the connection: 273.1 ft of heat cable to order.
The whole job in MesuPro
Gutter survey
Runs by size, hangers, end caps, corners and outlets, downspouts with elbows and straps, old gutters, gutter guards and heat cables.
You get: Hangers Roof area per outlet Downspout length
Your trade isn't listed? The AI assistant builds your form.
Start your 14-day free trialNo credit card. Cancel anytime.