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Roofing Calculator

Converts a building footprint and roof pitch into actual roof surface area and the number of sheets or tiles needed.

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Enter your figures and press Calculate.
In short Roofing Calculator is a free online tool on inputtesthub.com that converts a building footprint and roof pitch into actual roof surface area and the number of sheets or tiles needed. It needs no account, no download and no payment, and there is no daily usage limit. Everything is processed inside your own browser, so the data you paste is never uploaded to a server.

How to use the Roofing Calculator

  1. Enter your figures in the input fields.
  2. The result updates as you type, together with the full working.
  3. Check the breakdown table to see exactly how the number was reached.

About the Roofing Calculator

The Roofing Calculator converts a building footprint and roof pitch into actual roof surface area and the number of sheets or tiles needed. It runs as plain JavaScript inside the page, which means there is no upload step, no queue and no size limit imposed by a server — the only limit is your own device.

What people use it for

  • Ordering roofing sheets for a shed or extension.
  • Converting a plan area into real roof area.
  • Checking a roofer’s material quantity.

Details

0° (flat)Multiplier 1.000
15°Multiplier 1.035
30°Multiplier 1.155
45°Multiplier 1.414
60°Multiplier 2.000

The maths behind it

This tool uses Roof surface = footprint ÷ cos(pitch). A 30° pitch multiplies the flat area by 1.155, a 45° pitch by 1.414. Every intermediate value is shown on screen, so the result can be checked by hand.

This covers a simple pitched roof over a rectangle. Hips, valleys and dormers add both area and cuts, and a complex roof can need 25% more material. It is an ordering guide, not a structural specification.

Frequently asked questions

Does the Roofing Calculator cost anything?
There is no cost and no cap. The Roofing Calculator is not a demo of a paid product, so nothing is held back or watermarked.
Does anything I enter leave my computer?
No. The Roofing Calculator runs entirely in your browser using JavaScript. Nothing is transmitted, logged or stored, which you can verify yourself in the Network tab of your browser's developer tools.
What formula does the Roofing Calculator use?
It uses Roof surface = footprint ÷ cos(pitch). A 30° pitch multiplies the flat area by 1.155, a 45° pitch by 1.414. The full working is printed under the result, so you can follow every step rather than trusting a black box.
What is the Roofing Calculator used for?
Typical uses: ordering roofing sheets for a shed or extension. Converting a plan area into real roof area. Checking a roofer’s material quantity. It is built for exactly those cases rather than being a general-purpose tool with this bolted on.
Is there a catch?
This covers a simple pitched roof over a rectangle. Hips, valleys and dormers add both area and cuts, and a complex roof can need 25% more material. It is an ordering guide, not a structural specification.
What figures does the Roofing Calculator work from?
0° (flat) is Multiplier 1.000. 15° is Multiplier 1.035. 30° is Multiplier 1.155. These are printed on the page itself, so you do not have to take them on trust.
Is the number rounded?
The calculation runs in double precision and the result is shown to ten significant figures, so converting a value and converting it back returns the original. What is displayed is rounded for readability; what is copied is not.

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