Job calculators
Room quantities, slope conversions and a horizontal level check.
Room dimensions
Use finished internal dimensions.
Includes 2 m² allowance.
Calculation notes
Floor area = length × width. Room volume = floor area × ceiling height. Use one consistent unit throughout; feet are decimal feet, so 6 ft 6 in is 6.5 ft.
This assumes a constant ceiling height and does not subtract openings or fixtures. Flooring pack sizes, tile layout and manufacturer guidance determine the allowance you actually need. A waste allowance is not a paint or heating calculation.
Convert a slope
Rise or fall relative to horizontal run.
Direction: rise. Ratio uses the magnitude of the slope.
Calculation notes
Percentage = rise ÷ horizontal run × 100. Angle = arctan(rise ÷ run). A 1:N ratio has a grade of 1 ÷ N. The run is the horizontal distance, not the sloping length.
As a check, 1:60 is 1.667% and approximately 0.955°. This is a unit conversion, not a recommendation for a drain, roof, accessible route or building regulation requirement.
180° horizontal check
Compare two marks on the same wall after rotation.
Use the manufacturer's check procedure for your instrument. This calculation assumes the mark difference represents twice the horizontal-axis error at the entered distance.
Estimate is within the entered tolerance
Maximum mark difference at this distance: 6 mm. Allow for line thickness and marking uncertainty.
Calculation notes
Estimated error at the wall = mark difference ÷ 2. Error per 10 m = estimated error × 10 ÷ wall distance. Repeat independently for each horizontal axis with a stable setup and the manufacturer's procedure.
This screens horizontal alignment only. It does not verify vertical lines, plumb, square, all laser planes or performance after a drop. An apparent pass is not a calibration certificate. Retest unexpected results and arrange service when required.