Free Construction Calculation Tools

Work out stair geometry, convert gradients and estimate slab or post-hole concrete volumes in your browser. Print the result with Chippy Tools worksheets.

Calculate quantities and geometry using your own measurements. These tools do not select the code, certify a design or size structural members. No signup is needed, and your measurements stay in your browser.

All measurements use millimetres or metres. The prefilled values are examples; replace them with your measurements.

Stair set-out

One straight flight with the upper floor acting as the final tread. Enter a riser count from your design; the result does not check code limits.

Riser = total rise ÷ riser count. Goings = risers − 1. Run = goings × going. Relationship = 2 × riser + going.

Read the worked example · Check stair rules by country

Gradient conversion

Convert an upward or downward slope's magnitude. Run means horizontal distance, not distance along the slope.

Enter 60 for a gradient of 1:60. Changing format converts the value you have entered.

Percentage = rise ÷ run × 100. Angle = arctan(rise ÷ run). Fall = horizontal run × gradient.

Read the conversion guide · Check ramp rules by country

Concrete quantities

Estimate a rectangular slab or identical round holes. Hole volume is gross excavation volume, before displacement by posts. Allowance is your estimating choice.

Enter the dimensions of one slab. Identical slabs are multiplied by the count.

Slab = length × width × depth. Round hole = π × (diameter ÷ 2)² × depth. Convert all dimensions to metres first.

Slab example · Post-hole example · Footing requirements

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