Clear numbers for dormer projects

Dormer Calculator exists for one reason: planning a dormer should not start with guesswork. Whether you are a homeowner weighing up a loft conversion or a builder preparing a quick budget, you deserve fast, honest numbers.

What we do

We build a free dormer calculator that turns width, depth, height, roof pitch and material into roof area, a materials list and a cost range. Every formula is published on the calculator page so you can check the work.

Alongside the tool, our blog explains costs, planning permission, roof geometry, insulation and design choices in plain language.

Our principles

• Transparent: formulas and assumptions are visible.
• Practical: results you can hand to a contractor.
• Honest about limits: estimates are not quotes, and we say so clearly.
• Accessible: fast, keyboard friendly and readable on any device.
• Independent: we do not sell leads or recommend specific contractors.

How we keep the site free

The site is supported by clearly labeled advertising. Ads never change calculator results or editorial content.