Square Footage Calculator
Add up the area of rectangles, triangles, circles and trapezoids in square feet or square metres, subtract cut-outs and add an allowance for waste.
Construction Calculators
Free construction calculators that estimate materials and quantities with clear formulas, worked examples and imperial or metric units. No sign-up needed.
Planning & budget
Renovation Cost Calculator
Build a renovation budget from your own line items with quantities and prices, then add a contingency and tax to see the total.
Concrete & masonry
Work out how much concrete to order for slabs, footings and columns, in imperial or metric units, with a waste allowance you control.
Concrete Calculator
Work out how much concrete you need for a slab, patio or footing in cubic yards or m³, plus how many 40, 60 or 80 lb bags to buy, waste included.
Rebar Calculator
Estimate rebar for a slab grid: bars each way, total length with laps and waste, weight from ASTM or metric sizes, and stock bars to buy.
Structure & framing
Stair Calculator
Work out riser height, number of steps, tread depth, total run and stringer length, with optional US IRC or Australian NCC limit checks.
Wall Framing Calculator
Estimate how many studs and how much plate timber you need for a wall, from its length, stud spacing, openings and corners, with waste.
Board Feet Calculator
Calculate board feet for lumber from thickness, width, length and quantity, with waste, cubic volume and a price per board foot estimate.
Roofing
Roof Pitch Calculator
Convert rise and run into roof pitch (x/12), degrees and percent slope, with rafter length, the area multiplier and sloped roof area.
Walls & finishes
Drywall Calculator
Estimate how many drywall or plasterboard sheets you need for walls and ceilings, minus doors and windows, plus screws, joint compound and tape.
Wallpaper Calculator
Work out how many rolls of wallpaper you need from wall widths and height, roll size and pattern repeat, with a trim allowance and waste.
Plaster and Render Calculator
Estimate plaster or render for walls and ceilings: volume from area and thickness, and kilograms and bags from the product’s consumption figure.
Flooring & tile
Tile, Grout and Adhesive Calculator
Calculate how many tiles, how much grout and how much tile adhesive you need from the area, tile size, joint width and depth.
Electrical
Voltage Drop Calculator
Calculate voltage drop for copper or aluminium wire by AWG or mm², single- or three-phase, with the NEC 3% and 5% recommendations for US circuits.
Heating & cooling
BTU Calculator for Room Air Conditioners
Find the BTU/h cooling capacity for a room air conditioner from room area, sun, occupants and kitchen use, using the ENERGY STAR sizing chart.
Plumbing & water
Rainwater Tank Calculator
Estimate how much rainwater your roof can collect each year and how long a tank lasts at your daily use, in litres or US gallons.
Solar & energy
Insulation R-Value and U-Value Calculator
Add up the thermal resistance of wall, roof or floor layers from thickness and conductivity to get RSI, the U-value and the US R-value.
Solar Panel Calculator
Estimate how many solar panels you need from your yearly electricity use, the specific yield for your location from PVWatts or PVGIS, and panel rating.
Outdoor & landscaping
Volume Calculator for Soil, Gravel & Fill
Calculate cubic yards, cubic metres or cubic feet of soil, gravel, mulch or fill for any area and depth, with a swell or shrink factor and weight.
Deck Calculator
Estimate deck boards, joists, fasteners and footings for a rectangular deck from its size, board width and gap, joist spacing and post spacing.
Fence Calculator
Estimate fence posts, pickets or panels, rails and bags of concrete for post holes from fence length, post spacing, gates and hole size.
Pavers Calculator
Estimate how many pavers you need for a patio or path, with base and bedding sand volumes, edge restraint length and an allowance for cuts.
Retaining Wall Block Calculator
Estimate blocks, caps, drainage gravel and drain pipe for a segmental retaining wall from its length, height and block size.
Asphalt Calculator
Work out how much asphalt you need for a driveway or path: volume from area and thickness, and tonnes from your supplier’s density.
Cut and Fill Calculator
Balance earthworks: compare cut and compacted fill volumes with swell and shrink factors to see the surplus to haul away or the fill to import.
Project management
Labor Hours Calculator
Estimate labor hours, crew days and labor cost for a job from your own task quantities and productivity rates, crew size and hourly rate.
Contractor Quote Comparison
Compare up to three contractor quotes line by line, see totals and the lowest price, and rank them with weighted scores for price, quality and schedule.
Construction Payment Schedule
Plan construction progress payments: split the contract into stages by percentage, see each payment, retainage held and whether stages add up to 100%.
Project Materials List
Collect material takeoffs from every construction calculator into one project list, total them by material, add prices and export to CSV.
Converters
Construction Unit Converter
Convert lengths between feet-and-inches fractions, inches, feet, metres and millimetres, and slopes between percent, degrees, x:12 pitch and 1-in-n.
Estimate before you buy
Most building projects go over budget for one of two reasons: the material order was wrong, or the plan changed halfway through. A good estimate fixes the first problem. These calculators help homeowners, DIYers and small contractors work out how much material a job needs before anyone visits a supplier.
Every calculator on this page follows the same rules:
- Units you can switch. Work in feet and inches or metres and centimetres. The numbers convert when you switch, so you can measure in one system and order in the other.
- Waste allowances you control. Real jobs lose material to cutting, spillage and uneven ground. Each tool lets you set the allowance and shows how it changes the order.
- The formula on the page. Each tool shows the formula, defines every variable and works through examples, so you can check the result by hand or explain it to a client.
- Nothing leaves your browser. All calculations run on your device. We do not store your measurements.
How to get accurate measurements
Measure twice, at the widest points, and write the numbers down as you go. For slabs and floors, check the thickness or depth in several places, because ground is rarely level. Split L-shaped or irregular areas into rectangles, calculate each one and add the results. For walls, measure the gross area first and then subtract doors and windows.
When to call a professional
These tools estimate quantities. They do not replace structural design, engineering calculations or local building codes. Load-bearing slabs, retaining walls, roofs and anything that needs a permit should be checked by a qualified engineer or builder. Use our estimates to prepare, to compare quotes and to ask better questions.