Construction Calculators
Free online construction calculators to estimate concrete, cement bags, bricks, blocks, mortar, plaster, rebar, steel, excavation, gravel, sand, asphalt, roofing and stairs before you buy materials or start work.
Every building project starts with quantities. Order too little concrete and the pour stops halfway; order too many bricks and the extra pallets eat into your budget. Our construction calculators turn your measurements into clear material estimates in seconds, so homeowners, contractors, site engineers, quantity surveyors and DIY builders can plan with confidence.
Each construction calculator on SZToolify focuses on one job. Enter length, width, depth or thickness in metres, centimetres, feet or inches, and get the volume, weight or count you need, with a sensible allowance for waste. Use them together to build a complete construction material estimate for slabs, footings, walls, roofs and stairs.
Concrete and cement calculators
Concrete is ordered by volume (cubic metres or cubic yards), while bagged cement and premix are bought by weight. These tools handle both, so you know exactly how much to order from the batching plant or the builders’ merchant.
Concrete Slab Calculator
Work out the concrete volume for floor slabs, patios, garage bases and shed bases from length, width and slab thickness.
Concrete Footing Calculator
Estimate concrete for strip footings and pad footings, including multiple pads of the same size.
Concrete Column Calculator
Calculate concrete for square, rectangular and round columns, piers and sonotube forms.
Concrete Volume Calculator
A general concrete volume calculator for any rectangular or cylindrical pour, in cubic metres, cubic feet and cubic yards.
Cement Bag Calculator
Find how many bags of cement, sand and aggregate you need for a chosen concrete mix ratio and bag size.
Foundation Calculator
Estimate concrete for house foundations, raft foundations and trench fill foundations in one place.
Concrete Block Calculator
Count the concrete blocks or cinder blocks (CMU) needed for a wall, with mortar and openings deducted.
Brick, mortar and plaster calculators
Masonry estimates depend on brick size, mortar joint thickness and wall thickness. These calculators account for all three, so your brick count and mortar quantity match how the wall will actually be built.
Brick Wall Calculator
Calculate the number of bricks for a wall of any size, minus doors and windows, for single or double skin walls.
Bricks per m² Calculator
See how many bricks fit in one square metre or square foot for your brick size and mortar joint.
Mortar Mix Calculator
Work out cement and sand quantities for bricklaying mortar at common mix ratios such as 1:4, 1:5 and 1:6.
Plaster Calculator
Estimate plaster or render for walls and ceilings from surface area and coat thickness.
Retaining Wall Calculator
Plan blocks, cap stones, base gravel and backfill for garden and landscape retaining walls.
Rebar and steel calculators
Steel is priced by weight, but drawings specify bar diameter, spacing and length. These tools convert one into the other.
Rebar Weight Calculator
Find the weight of reinforcement bars by diameter and length, in kg per metre and lb per foot.
Steel Weight Calculator
Calculate the weight of steel plates, flats, round bars, pipes and sections for ordering and transport.
Reinforcement Calculator
Estimate the number of bars, total length and total weight of reinforcement for a slab from bar spacing.
Earthwork, aggregate and paving calculators
Excavation Calculator
Calculate dig volume for trenches, basements and pits, including bulking of loose soil for skip and truck hire.
Gravel Calculator
Convert area and depth into gravel volume and tonnes for sub-bases, paths and drainage.
Sand Calculator
Estimate sand in cubic metres, tonnes or bags for bedding, concrete mixes and fill.
Asphalt Calculator
Work out how many tonnes of asphalt (tarmac) are needed for a driveway or car park at a given thickness.
Roof and stair calculators
Roof Pitch Calculator
Convert rise and run into roof pitch, angle in degrees and slope percentage.
Roof Area Calculator
Find the true sloped roof area from the building footprint and pitch, ready for tile and sheet estimates.
Stair Stringer Calculator
Calculate the number of steps, riser height, tread depth and stringer length from total rise.
Stair Angle Calculator
Check the pitch of a staircase from rise and going to see whether it suits comfortable everyday use.
Project estimating calculators
Material Estimator
Combine concrete, masonry, steel and aggregate quantities into one construction material list.
Construction Cost Estimator
Turn material quantities and your local unit prices into a total project cost, with labour and contingency.
How to use our construction calculators
- Measure the job. Take length, width and depth (or height) from your drawings or on site, and note openings such as doors and windows.
- Pick your units. Enter metres, centimetres, millimetres, feet or inches. Each calculator converts units for you.
- Add a waste allowance. Most trades add 5–10% for concrete and 5–15% for bricks, blocks and tiles to cover breakage, cutting and uneven ground.
- Read the results. Get volume, weight, count and number of bags, then use the cost estimator to price the job.
Why estimate materials with a calculator?
Manual take-offs are slow and easy to get wrong when you switch between units or forget to deduct openings. A dedicated building material calculator applies the same formula every time, shows the result in the units your supplier uses, and makes it easy to compare options, such as a thicker slab against extra reinforcement, before you spend money.
The results are estimates for planning and budgeting. For structural elements like foundations, retaining walls and reinforced slabs, always follow your engineer’s drawings and local building regulations.
More building and lumber calculators
Retaining Wall Block Calculator
Estimate blocks, cap blocks and gravel backfill for a retaining wall.
Board Foot Calculator
Calculate board feet and lumber cost from thickness, width and length.
Mortar Calculator
Estimate mortar volume and bags for brick and block walls.
Rafter Length Calculator
Get rafter length from roof pitch and run.
Cubic Yard Calculator
Convert length, width and depth into cubic yards for concrete, soil and gravel.
Frequently asked questions
How do I calculate how much concrete I need?
Multiply length × width × thickness, with all three in the same unit, to get the volume. For example, a 4 m × 3 m slab that is 0.1 m thick needs 1.2 m³ of concrete. Add 5–10% for spillage and uneven sub-base. The Concrete Slab Calculator does this for you in metric or imperial units.
How many bricks are in one square metre?
For a single-skin wall using standard UK bricks (215 × 102.5 × 65 mm) with a 10 mm mortar joint, it is about 60 bricks per square metre. US modular bricks work out at roughly 6.75 bricks per square foot. Other brick sizes give different numbers, which the Bricks per m² Calculator handles.
Should I add extra material for waste?
Yes. A typical allowance is 5–10% for concrete and aggregate and 5–15% for bricks, blocks and tiles. Use the higher end for complicated shapes, lots of cuts or inexperienced crews.
Do the calculators work in both metric and imperial units?
Yes. You can enter measurements in metres, centimetres, millimetres, feet or inches, and results are shown in the units suppliers commonly use, such as cubic metres, cubic yards, tonnes or bags.
Are these construction calculators free?
All SZToolify calculators are free to use, need no signup and run in your browser on desktop, tablet and mobile.
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