Free tools · Gapeye
Trade Calculator Hub
Quick site maths for trades, DIY and property professionals. Results are estimates — always confirm on site with a tape measure and level.
Cubed Volume (W × H × D) Calculator
Enter width, height and depth to get volume and estimated 20 kg concrete/screed bags (~0.01 m³ per bag + 10% wastage).
- m³
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- Litres (L)
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- cm³
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- ft³
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- Estimated 20 kg bags
- 0
Buy materials:
Spirit Level Slope, Fall & Gradient Calculator
Enter run length and slope to get total drop/rise, gradient, percentage, angle and the shim/packer height needed.
- Total drop / rise (mm)
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- Gradient (mm/m)
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- Percentage (%)
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- Angle (°)
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- Shim / packer height needed (mm)
- 0
Drainage fall reference: 1:40 = 25 mm/m · 1:80 = 12.5 mm/m
Door, Window & Fire-Door Frame Diagonal Squareness Calculator
Enter frame width, height and both measured diagonals to check squareness.
- Theoretical square diagonal √(W² + H²) (mm)
- 0
- Diagonal difference |D1 − D2| (mm)
- 0
- Verdict
- —
UK/EU fire doors (FD30/FD60): keep a 2–4 mm top/side perimeter gap, 3 mm target with intumescent strips. Always follow the door certification.
Calculator FAQ
How many 20 kg bags do I need per cubic metre?
Roughly 100 bags per m³ (~0.01 m³ per bag); the calculator adds 10% wastage.
What fall does a drain need?
Common references are 1:40 (25 mm/m) and 1:80 (12.5 mm/m); check local regulations.
How square should a door frame be?
A diagonal difference of 2 mm or less is square; 2–5 mm is a minor rack; over 5 mm is out of square.