Concrete calculators
19 concrete calculators: volume, formwork area, mix ratio, cement quantity, pour sections, curing time, joint spacing, mass concrete temperature, admixtures and blinding.
▦Concrete Volume CalculatorEnter length, width and thickness to get the concrete volume you need and how many truck loads that is.◎Concrete Mix Design CalculatorWork out cement, sand, gravel and water per cubic metre from the target grade and water-cement ratio.◍Cement Quantity CalculatorGet total cement, bag count and the cement/fly-ash split for a given volume and grade.▥Formwork Area CalculatorPick a member type, enter section and length, and get the formwork contact area plus sheet and batten estimates.◐Concrete Curing and Maturity CalculatorTurn curing temperature into maturity and equivalent age, and check the code minimum.▭Post-Cast Strip CalculatorEnter strip length, width, slab thickness and waterstop size to get concrete volume plus waterstop length and weight.◎Mass Concrete Temperature CalculatorPlacement temperature, adiabatic rise and peak temperature in one step.▤Concrete Pour Sequencing CalculatorDivide a slab into strips and get the volume, truck count and duration for each pour.⊞Concrete Strength ConverterConvert between grade, MPa, psi and kgf/cm², with cube-to-cylinder correction.▥Concrete Saw Cut Spacing CalculatorJoint spacing, saw depth and the sawing window from slab thickness.≡Concrete Yield CalculatorConvert batch weights and density into actual yield and per-m³ contents.▽Concrete Pumping CalculatorReal output, pour duration and the truck fleet needed to keep the pump fed.◧Site Mix Adjustment CalculatorEnter the lab mix and moisture content to get real batch weights.◈Admixture Dose CalculatorPercentage dose to kg per m³ and per batch, with the new w/b ratio.▥Grout Quantity CalculatorVolume, weight, bags and water in one pass.◭Shotcrete Quantity CalculatorBack-calculate batched volume and material use from rebound.▤Strip Footing CalculatorConcrete, blinding, formwork and base area for strip footings.▦Pile Cap CalculatorConcrete, two-way bottom steel, formwork and blinding per cap.▭Blinding and Cushion CalculatorPlan size, concrete volume and side formwork for blinding.
What this group solves
Concrete is the material where estimating errors cost the most: a cubic metre short means a cold joint or a second small pour, a cubic metre over is money in the skip, and once it starts to set there is no rework. These tools cover the whole chain — volume from the concrete volume calculator, formwork area, cement and aggregate from the mix ratio and cement quantity calculators, then curing and striking times to plan the sequence.
The two things most often missed on site are waste and temperature. Volume results already carry a waste allowance you can tune for pumping, direct discharge or barrows, and there is a separate tool for mass concrete that estimates peak core temperature and the core-to-surface differential from placement temperature, heat of hydration and ambient conditions. Blinding, strip footings, pile caps and construction joints each have their own tool rather than being forced through a generic volume formula.
The order of use is fixed: volume with waste first, then split it into materials, then the process parameters (pour sequence, curing, joint spacing, temperature). Do it the other way round and you re-order — by the time you notice the waste allowance is missing, that pour has already gone out, and the shortfall needs its own small delivery.
Which one for your case
| You have member dimensions and need volume plus truck counts | Concrete Volume Calculator |
| Grade is fixed — how much cement, sand and gravel per cubic metre | Concrete Mix Design Calculator |
| Only area and thickness known, need cement by the bag | Cement Quantity Calculator |
| The pour will not finish in one go — how to split it | Concrete Pour Sequencing Calculator |
| Worried about cracking — joint spacing and curing days | Concrete Saw Cut Spacing Calculator |
| Mass concrete (over 1 m thick) and the core-to-surface differential | Mass Concrete Temperature Calculator |
| Aggregate got wet and the added water must be corrected | Site Mix Adjustment Calculator |
Where this group goes wrong
- Reporting the net drawing volume with no waste. Pumped placement runs 1-2%, direct truck discharge 2-3% and barrows 3-5%. On 100 m³, 3 m³ short means a separate small delivery, and the part-load surcharge usually exceeds the cost of the concrete itself.
- Using a C30 mix design to price a C25 pour. Cement differs by roughly 40 kg/m³, so a 150 m³ slab is 6 t of cement out.
- Estimating formwork from floor area. Beam sides, slab soffits and all four column faces all count — housing typically lands at 2.5-3.5 m² of formwork per m² of floor, so using floor area cuts the quantity by more than half.
- Adjusting the water/cement ratio by volume. Water is batched by mass, and sand at 5% moisture brings about 40 kg of water per cubic metre. Ignore it and the real ratio runs 0.05 high, which drops the strength a whole grade.
FAQ
How do I calculate concrete volume?
Length × width × depth for a slab or rectangular element, π × radius² × depth for a column or pile. Break irregular shapes into simple blocks and add them. Then add waste: 1-2% for pumped concrete, 2-3% for direct discharge, 3-5% for barrow work, at the top of the range for blinding and slabs where level control is loose.
How much cement, sand and aggregate per cubic metre?
It depends on grade and mix design. A typical C25 mix uses about 370-400 kg cement, 580-620 kg medium sand, 1250-1280 kg crushed stone and 175-185 kg water per cubic metre. Use the mix ratio calculator for your grade and cement type, then the cement quantity calculator to convert to 50 kg bags.
When can formwork be struck?
Side forms after about 24 hours once strength reaches 1.2 MPa. Soffits depend on span: 50% of design strength up to 2 m, 75% for 2-8 m, 100% beyond 8 m — roughly 3, 7 and 28 days at 20°C. In cold weather go by companion cubes, not by the calendar.
Should I book 6, 9 or 12 m³ trucks?
It depends on access and discharge, not on unit price. 6 m³ suits tight sites and small pours, 9 m³ is the usual workhorse, and 12 m³ means fewer trips but needs room to manoeuvre, adequate pumping and enough time to discharge before initial set — anything left in the drum is wasted. Below about 20 m³ the part-load surcharge usually outweighs any haulage saving, so pick whichever size delivers in one go.
How much does a cubic metre of concrete weigh?
Take 2400 kg/m³ for plain concrete, 2500 kg/m³ for reinforced, and 1800-1950 kg/m³ for lightweight aggregate. You need this for floor loading, formwork pressure and truck payload. Pumped mixes run 2380-2420 kg/m³ because of the higher sand content.
How many days before formwork can be struck?
Side forms come off at 24-48 h in normal weather, as soon as edges will not spall. Soffit forms follow the matching-cured cube strength: 50% for spans up to 2 m, 75% for 2-8 m and 100% above 8 m. C30 at 20 °C reaches about 75% in 7 days; in winter allow 10-14.
Why do blinding, strip footings and post-cast strips need their own tools?
Their sections do not match a plain box. Blinding projects 100 mm past the footing each side, strip footings are trapezoidal, and a post-cast strip adds a waterstop plate plus formwork left in on both faces. Running them through a generic length × width × depth understates blinding by 10-15%.
Related data tables
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Results are estimating aids only and are not a design basis. Construction and final accounts must follow the drawings, the applicable standards and an approved method statement. Anything affecting structural safety, shoring or falsework must be checked by a suitably qualified engineer.