Methodology

This page explains how the calculators are built and checked, so you can judge how much to trust a result.

Standard formulas

Each calculator uses a standard, published formula for its job, such as volume divided by 27 for cubic yards, or run times the slope factor for a rafter. The formula and a worked example are shown on every calculator page.

Testing

Every calculator is tested against known examples with a fixed, expected answer before it goes live, and those checks run again on every update, so a change cannot quietly break the maths.

Reference figures

Some results use reference figures, such as the weight of a cubic yard of gravel or the number of bricks per square metre. These vary with the product, the moisture and the country, so they are approximate and are labelled as estimates. We use commonly published values and will refine them as we gather better sources.

Units and rounding

Calculators work in both imperial and metric, and convert between them. Results are rounded for display, while the underlying maths uses full precision, so a hand check may differ in the last digit.

What we do not include

The calculators estimate material quantities and material cost. They do not include labour, delivery, adhesive, grout or engineering design unless a page says so. For structural work, consult a qualified professional.

Reporting an error

If a result looks wrong, email foremancalc@gmail.com with the calculator name and the numbers you entered, and we will check it.