Roofing Calculator

How to use Roofing Calculator

1. Open Roofing Calculator in your browser — it loads instantly and works offline once cached.
2. Enter your values in the input fields. Every field is labelled so you know exactly what to type.
3. The result updates automatically as you type — there is no "submit" round-trip to a server.
4. Adjust any input to compare scenarios and see how the outcome changes in real time.
5. Copy or note the result. Nothing you enter is stored or sent anywhere.

Why use Roofing Calculator?

• 100% free with no limits, no sign-up and no watermarks.
• Private by design — your data are processed in your browser and never uploaded to a server.
• Fast and lightweight, with instant results even on a phone or a slow connection.
• Works everywhere — any modern browser on Windows, macOS, Linux, Android or iOS.
• Part of a full construction suite, so related roofing tasks are one click away.

What people use Roofing Calculator for

• Estimating roofing material for a pitched or flat roof.
• Working out true roof area from a building footprint.
• Costing a re-roofing job.

Roofing Calculator: limits and things worth knowing

• The roof area is larger than the building footprint because of the pitch. Divide the footprint by the cosine of the pitch angle — a 30-degree roof has about 15% more area than its plan view.
• Add for overhangs, ridges, hips, valleys and verges, all of which need extra material and specific components.
• Waste allowance is typically 10-15%, higher on complex roofs with multiple hips and valleys.
• This is a material estimate only. Structural loading, fixings and ventilation are design matters for a qualified professional and are governed by building regulations.

Is it private and secure?

Your privacy is built in. Roofing Calculator runs completely on your device, so whatever you enter stays in your browser and is never transmitted, logged or stored on any server.

Network activity: none. Nothing is sent and nothing is fetched. This tool makes no network request at all once the page has loaded — which is why it keeps working if your connection drops.

You do not have to take that on trust — our privacy proof page publishes the Content-Security-Policy that enforces it, lists every third party it permits, and shows how to verify the whole claim yourself.

Learn more

Why Browser-Based Tools Are Safer for Your Files — Most online converters upload your files to a server. Client-side tools don't. Here's why that difference matters for privacy.