Gutter tools
Four calculations settle most gutter projects: linear footage, drainage area and required gutter size, downspout count, and the guard break-even. None of them need a contractor, and running them yourself is the fastest way to tell a fair quote from an inflated one.
Linear footage. Measure every eave that will carry gutter. This is the divisor for every quote you receive.
Sizing. This Old House's method uses drainage area, a roof pitch factor from about 1.0 (flat) to 1.3 (12-in-12), and local rainfall intensity in inches per hour. Five-inch K-style covers roughly 5,520 square feet of drainage area; 6-inch about 7,960.
Downspouts. Roughly one square inch of downspout cross-section per 100 square feet of roof. A 2x3 handles about 600 square feet, a 3x4 about 1,200, a 3-inch round about 706 and a 4-inch round about 1,255.
Guard break-even. Guard quote divided by annual cleaning spend equals payback in years. With guards at about $40 per linear foot and cleaning at $191-$529 per visit, this calculation kills a lot of guard sales on its own - which is exactly why you should run it before the sales visit, not during.
Choosing gutters tools
The judgement calls that decide the bill, before anyone quotes you.
- Measure before you call anyone Knowing your footage changes how quotes are presented to you.
- Treat calculators as sanity checks They tell you whether a quote is in the right universe, not what your exact job costs.
- Use local rainfall intensity Sizing that ignores your regional rainfall rate will under-size in storm-prone areas.
- Run the break-even before the pitch Deciding in advance is the single most effective defense against a high-pressure close.
- Recheck downspout count It is the cheapest capacity fix and the most commonly skimped item on a bid.
All gutters tools
Gutter Cost Calculator
Gutter Size Calculator
Gutter Guard ROI Calculator
Downspout Drainage Planner
Where these figures come from
Sources last checked
- This Old House - How To Size Gutters and Downspouts · retrieved 2026-07-25
- This Old House - Gutter Guard Installation Cost (2026 Pricing) · retrieved 2026-07-25
- This Old House - How Much Does Gutter Cleaning Cost? 2026 Pricing · retrieved 2026-07-25
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