Construction Calculators

Getting a materials estimate wrong on a build is expensive in both directions: order too little and the job stalls waiting on a second delivery, order too much and money sits in the yard as waste. The construction calculators on this page turn the handful of measurements you already have — a length, a width, a thickness, a mix ratio — into the quantities you actually buy: board feet of lumber, cubic yards of concrete, bags of cement, and gallons of paint or sealant. Every tool works in both imperial and metric and converts your entered numbers in place when you flip the unit toggle, so a plan drawn in feet and a spec sheet written in metres never force you to start over. **Lumber.** The board foot calculator measures hardwood and rough-sawn lumber the way suppliers price it — by volume, not by length. One board foot is a piece one foot square and one inch thick (144 cubic inches), so a 2‑inch by 6‑inch board eight feet long is not eight board feet but eight. The calculator handles the thickness‑times‑width‑times‑length arithmetic and multiplies by your piece count, which is where hand estimates usually slip. **Concrete and cement.** These two tools answer different questions and are easy to confuse. The concrete calculator sizes a pour — a slab, footing, or path — giving you the total volume in cubic yards or cubic metres and the number of pre‑mixed bags it would take, including the roughly five to ten percent you should add for spillage and uneven subgrade. The cement calculator goes one level deeper for mix‑from‑scratch work: from your slab dimensions and a mix ratio such as 1:2:4, it estimates the dry volume (wet concrete shrinks, so dry material is counted at about 1.54 times the finished volume) and splits it into bags of cement, plus the sand and aggregate that go with them. Use the concrete calculator when you are buying bags of ready mix; use the cement calculator when you are batching your own. **Coverage.** The gallons‑per‑square‑foot calculator estimates how much paint, primer, stain, or sealant a surface needs. Enter the area (or a length and width) and the product's spread rate — most wall paints cover around 350 square feet per gallon on a smooth surface, less on rough or porous material — and choose how many coats. Rough block, bare drywall, and exterior masonry all drink more than the label promises, so round up. Every calculator here runs entirely in your browser, keeps your numbers on your device, and needs no sign‑up. Treat the results as buying estimates: measure twice, add a waste margin for offcuts and overpour, and confirm mix ratios and coverage rates against the specific product and local building code before you place an order.