Free DIY Calculators
Quick, honest math for real projects — set your speeds, size up a lumber order, or buy the right amount of paint. Each tool shows the exact formula behind its answer, so you can check our work.
Drill Speed Calculator: The Right RPM for Any Material
RPM = 3.82 × SFM ÷ DFind the correct drill speed for steel, aluminium, plastic and more. Pick a material and bit size, and the calculator returns a recommended RPM and a safe working window — with the cutting-speed formula shown in full.
Open toolBoard Foot Calculator: Measure Lumber Like a Pro
BF = (T × W × L) ÷ 144Work out exactly how much lumber a project needs — and what it will cost. Enter thickness, width, length and quantity, and the calculator returns total board feet with the formula laid out in full.
Open toolPaint Calculator: How Much Paint to Buy for a Room
Gallons = area × coats ÷ 350Stop guessing at the paint store. Enter your room's size, doors, windows and number of coats, and the calculator returns the gallons to buy — with the area-and-coverage formula shown step by step.
Open toolThese calculators are guides for planning, not a substitute for manufacturer specs or local building codes. Always double-check critical measurements before you cut, drill or buy.