Free calculators for home improvement and DIY projects. Paint coverage, pool chemistry and more, all updated for 2026.
Home improvement projects are notorious for cost overruns, and one of the biggest sources of waste is buying too much or too little material. Our calculators help you estimate precisely what you need before you visit the hardware store. The Paint Coverage Calculator accounts for wall area, doors, windows, and number of coats. The Pool Chemical Calculator balances chlorine, pH, and alkalinity based on your pool volume. Getting the math right saves money and avoids multiple trips to the store.
Paint coverage depends on the type of paint, the surface texture, and whether you are applying a primer coat. Standard interior latex paint covers approximately 10 to 12 square metres per litre on smooth walls. Textured surfaces and dark-to-light colour changes may require additional coats, reducing effective coverage by 20 to 30 percent. Our calculator uses industry-standard coverage rates and lets you subtract door and window areas to give you the exact number of litres (or gallons) needed.
Maintaining balanced pool water prevents algae growth, protects equipment, and keeps swimmers safe. The three key parameters are free chlorine (1 to 3 ppm), pH (7.2 to 7.6), and total alkalinity (80 to 120 ppm). Our Pool Chemical Calculator converts your pool dimensions into volume, then calculates the exact dose of chlorine, pH adjuster, or alkalinity increaser needed to bring your levels into the ideal range. No more guessing with chemical dosing.