About

Build With Math makes free, simple calculators for decks, footings, concrete and other home building jobs. Each one answers a practical question, such as how far a joist can span or how many bags of concrete a post needs, and shows the numbers behind the answer.

Who checks the calculators

Every calculator is built and checked by Engr. Abdul Latif, a registered professional engineer (Ir.) working in civil and structural engineering. The calculators follow the International Residential Code (IRC) and the American Wood Council's deck guide (DCA 6), and each page explains its assumptions.

How to use this site

The calculators are for planning, budgeting and learning. Building rules differ between cities and counties, so always confirm sizes with your local building department and get a permit where one is required. For anything unusual, such as heavy loads, steep slopes or poor soil, ask a local licensed engineer.

Found a problem?

If you spot an error or want a new calculator, please use the contact form at the bottom of any page. Every message is read.