How Many Roofing Sheets Do You Need? A Step-by-Step Calculation Guide

One of the most common questions we get at Egesa Mabati is: "How many sheets do I need for my roof?" Getting this number right saves money and prevents costly delays from running short mid-project.

The Basic Formula

Roofing sheet quantity depends on four factors: roof length, roof width, roof pitch (slope angle), and the effective coverage width of your chosen sheet profile.

1. Measure the roof footprint — length and width at the base.
2. Account for pitch — a steeper roof has a longer actual slope length than the flat footprint suggests. A 22-degree pitch (typical in Kenya) adds roughly 8% to your slope length.
3. Divide by coverage width — each profile has a different usable (overlapped) width, typically 686mm–840mm.
4. Add overlap allowance — sheets overlap by about 100–150mm at each join.

Use Our Free Calculator

Rather than calculating by hand, try our interactive roof calculator — just enter your roof dimensions and pitch, select a product, and get an instant material list and cost estimate.

Always Add a Buffer

We recommend ordering 5–10% extra sheets to account for cutting waste around chimneys, vents, and roof valleys.