Gutter Length Calculator
Feet of gutter and downspouts needed for a roof.
Enter your values
Enter the roofline eave length (total) in ft.
Enter the downspout spacing in ft.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Gutter needed
- 150 ft
- Downspouts needed
- 5
- End caps needed
- 4
- 10-ft gutter sections
- 15
Quick answer
Gutter length equals your roof's eave perimeter; downspouts are typically one per 30-40 feet of gutter run.
downspouts = ceil(gutter length / 35)
At a glance
| What it does | Feet of gutter and downspouts needed for a roof. |
|---|---|
| Category | Home & DIY |
| Inputs needed | Roofline eave length (total), Downspout spacing |
| Main output | Gutter needed |
| Formula | downspouts = ceil(gutter length / 35) |
| Cost | Free — no sign-up, no download |
How to use the Gutter Length Calculator
- 1Measure the total length of eaves where gutters will be installed.
- 2Use a downspout every 30-40 feet of gutter run for good drainage.
- 3Buy gutter in standard 10-ft sections plus corner and end cap pieces as needed.
Inputs explained
- Roofline eave length (total)(ft)
- Enter the roofline eave length (total) in ft.
- Downspout spacing(ft)
- Enter the downspout spacing in ft.
Worked example
Using the values the calculator loads with:
Inputs
- Roofline eave length (total)150 ft
- Downspout spacing35 ft
Results
- Gutter needed150 ft
- Downspouts needed5
- End caps needed4
- 10-ft gutter sections15
Frequently asked questions
How many downspouts does a typical house need?
Most homes need one downspout per 30-40 feet of gutter, so a typical house has 4-6 downspouts total.
What size gutters should I use?
5-inch K-style gutters are standard for most homes; larger roofs or heavy rainfall areas may need 6-inch gutters.
What do I need to enter into the Gutter Length Calculator?
Just 2 values: roofline eave length (total), downspout spacing. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Gutter Length Calculator work out the answer?
Gutter length equals your roof's eave perimeter; downspouts are typically one per 30-40 feet of gutter run. It applies the formula downspouts = ceil(gutter length / 35) and shows the working so you can check each step by hand.
Is the Gutter Length Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.