Home and Energy Calculators
These calculators help homeowners and DIY builders plan jobs around the house. Work out a roof’s pitch, estimate the concrete for a slab, and explore the cost and payback of a solar system. Every tool is free and runs in your browser.
Calculators in this group
Who these calculators are for
Homeowners planning a project and wanting a rough number before they ask for quotes.
DIY builders who need quantities, such as the concrete for a pad or the length of a rafter.
People comparing solar options who want to understand cost and payback.
How these calculators work
Each page explains its formula in plain words, with a worked example and a list of assumptions and limits. Prices, sun hours and rates start as placeholders that you can change, and everything you type stays in your browser.
Tips for accurate results
Measure carefully and use the same unit for every length. Use your own quotes, bills and local figures instead of the defaults, because prices and sun hours differ by place. Real jobs also depend on shade, roof direction, ground conditions, reinforcement and local rules, which a simple calculator cannot see. Treat each result as an estimate and ask a local professional or supplier before you order materials or sign a contract.
How to choose the right calculator
Start with the job in front of you. Use the roof pitch calculator when you need the slope or rafter length for a roof. Use the concrete slab calculator when you are planning a pad and want to know how much to order. If you are thinking about solar, begin with the solar panel cost calculator to size a system and estimate its price, then use the solar payback calculator to see how long the savings might take to cover that cost.
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How Much Concrete Do I Need for a Slab? A 10×10 Example
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More answers
New to the tools? Read the FAQ page, and see the Disclaimer for the limits of the results. You can also browse all calculators.