Gutter Calculator

About this gutter calculator

Gutter quantity starts from one measurement: the total length of roof edges that get gutters — usually the eaves on the front and back of the house, plus any low sides, but not gable ends without eaves. A rectangular house measures 2 × (length + width) around the roofline: a 40 × 25 ft house has a 130 ft roofline, which is 13 ten-foot sections and 4 downspouts at 35-foot spacing. Our gutter guide covers measuring, 5-inch vs 6-inch sizing, and corner rules.

Downspout spacing is the rule that prevents overflow: one downspout every 30–40 feet of gutter, never more than 50 feet per run, plus one near each outside corner and one at each side of a valley. More downspouts cost a little more but reduce overflow risk in a downpour — and a long run with a single downspout at one end is the most common gutter sizing mistake.

Size follows roof and rain: 5-inch gutters are standard for most homes, while 6-inch gutters suit steep roofs and heavy-rain regions (a 5-inch K-style gutter carries much more than a 5-inch half-round of the same label, so profile matters too). Hangers run one every 2 feet. Seamless gutters, cut on site to eliminate most seams, cost more than sectional but leak less — sectional runs about $2–$5 per foot in materials, seamless installed about $4–$10.

How to use

1. Walk the house and add up every roof edge that will carry a gutter in feet (eaves, not gable ends).
2. Enter your section length (10 ft is standard for sectional gutter) and your downspout spacing (35 ft is typical).
3. Optionally enter the price per linear foot, then press Calculate.

Good to know

• Counts gutter length, sections, downspouts, and hangers only — corners (miters), end caps, elbows, and downspout extensions are separate fittings.
• Assumes one gutter run per edge; houses with multiple roof levels and valleys should be measured per roof section and added.
• Does not size gutter capacity for your roof area and rainfall — for steep roofs or heavy-rain regions, confirm 5-inch vs 6-inch sizing against local guidance.