Gutter Calculators

The deterministic sizing & quantity cluster — the highest-demand gutter queries: a gutter linear-feet calculator (sum of the eave runs), a gutter SIZE calculator (smallest size whose drainage area ≥ your effective roof area, from the labeled rainfall × gutter-size table), a downspout count calculator (drainage area or the 30–40 ft rule), a sections / hangers / end caps / corners / elbows calculator, a gutter slope calculator, a roof-pitch drainage-area calculator, and a gutter capacity / flow reference. Roof-pitch, rainfall and drainage-per-size figures are labeled published typicals, not a certified design — follow local code and the manufacturer's data.

Measure your eave runs and confirm capacity, spacing and coverage against the exact product you buy. Allow extra for corners, waste and slope (~5–10%). Sizes, capacities, spacings and panel lengths vary by product and brand — read the label and the manufacturer’s data.
Typical published planning values — NOT a certified design. Actual gutter sizing depends on local rainfall intensity, roof geometry, valleys and debris; follow local code and the manufacturer’s data, and consult a pro for complex roofs. Structural roof-load, ice-dam / heat-cable and foundation/yard drainage are set by code and a professional — not engineered here.
Gutter linear-feet calculatorAdd up to six eave runs to get the total linear feet of gutter you need. Free, instant, with the formula, a worked example and the corners-and-waste rule.Gutter size calculator (5" vs 6")Do you need 5-inch or 6-inch gutters? Enter roof footprint, pitch and rainfall to get the smallest K-style or half-round size that drains it.Downspout count calculatorHow many downspouts do you need? Runs both methods — roof area per outlet and the 1-per-30-to-40-ft rule — and recommends the larger, safer count.Gutter sections & materials calculatorTurn gutter linear feet into a parts list: 10-ft sections, hangers, end caps, corners and downspout elbows, with the formula and a worked example.Gutter slope calculatorHow much slope should a gutter have? Enter the run length and pitch to get the total drop in inches, with the ¼-to-½-inch-per-10-feet rule and a worked example.Roof-pitch drainage-area calculatorConvert a roof footprint into the effective drainage area for gutter sizing. Enter footprint and pitch to apply the SMACNA pitch multiplier.Gutter capacity / flow referenceHow much roof can a 5-inch or 6-inch gutter drain? Set the rainfall intensity to see the max roof area per gutter size, K-style and half-round.

Every Gutter Calculators tool is calculated server-side — visible immediately — with its formula, a worked example and a reference table, and works on the measurements you take and the prices you enter from your own quotes. Background reading is in the guides.