How to use this calculator
- Enter Total eave length in ft.
- Enter Ft per downspout in ft.
- Press Calculate. The highlighted row is your order quantity; the note beneath it translates the number into real-world terms.
Formula & constants
Gutter runs equal total eave length. One downspout per 30–40 ft of gutter; K-style 5 in handles most homes, 6 in for large or steep roofs. Sections come in 10 ft lengths. Every default in the fields above is editable — when your supplier’s spec sheet lists a different density, coverage rate or price, enter that number instead. The waste and compaction allowances follow common trade practice; see our methodology page for the derivation of each formula and the standards it references.
Where this fits in the project
Roof takeoffs start from the footprint corrected by pitch: get true area from the roof square footage calculator, convert to squares, then to shingle bundles or metal panels. Size gutters from the same perimeter measurement.
How this connects to your project
No quantity stands alone — each material in the chain depends on the ones around it. These are the planning steps that pair with the gutter calculator:
- Roofing Calculator — Gutters run along the roof perimeter.
- Roof Square Footage Calculator — Roof perimeter from area determines gutter length.
- Roof Pitch Calculator — Steeper roofs shed water faster, affecting gutter sizing.
- Rainwater Harvesting Calculator — Gutters channel water to rain barrels or collection systems.
- French Drain Calculator — Downspouts may feed into French drains for dispersal.
- Roofing Cost Calculator — Gutter replacement is often done with roofing.
Frequently asked questions
5 in or 6 in gutters?
5 in K-style drains most roofs; go 6 in when roof area per downspout exceeds ~750 sq ft or pitch is steep.
How much slope do gutters need?
1/4 in per 10 ft toward the downspout — visually level, hydraulically functional.
Last verified: — prices reflect current national averages. See our methodology.
Estimates are for planning. Material densities, coverage rates and prices vary by region and supplier — confirm final quantities before ordering, and check local code where structural or electrical work is involved.