Construction Calculators
20 free calculators.
Air ChangesWork out air changes per hour from room volume and ventilation airflow.Backfill VolumeWork out backfill needed by subtracting the buried structure volume from excavation volume.Beam Span RoughGet a very rough beam depth guide from span length. This is not a structural design.Ceiling AreaCalculate ceiling area from room length and width for boards, paint or panels.Circuit LoadCheck load in amps and as a percentage of circuit capacity from watts and voltage.Door Trim LengthEstimate trim length for door casings from door width, height and door count.Excavation VolumeCalculate dug volume from length, width and depth, plus a loose-volume figure after digging.Joist CountCount floor or ceiling joists along a run at a given spacing, including both end joists.Lighting Lumens NeededEstimate total lumens needed for a room from floor area and target light level in lux.Outlet Count RoughEstimate a rough number of wall outlets from total wall length and spacing between outlets.Plumbing Pipe LengthEstimate total pipe to buy from a straight run plus a percentage allowance for fittings and bends.Rebar QuantityCount how many bars fit along a length at a given centre-to-centre spacing.Rebar WeightEstimate the total weight of reinforcing bars from length, bar count and weight per metre.Roof Pitch AngleTurn roof rise and run into a pitch angle in degrees and a pitch ratio.Room VolumeCalculate the volume of a rectangular room from length, width and height.Subfloor AreaCalculate subfloor area with a waste allowance and an approximate sheet count.Truss CountCount roof trusses along a building length at a given spacing, including both end trusses.Ventilation CFMEstimate required ventilation airflow in cubic feet per minute from room size and air changes.Wall Area Minus OpeningsFind net paintable or coverable wall area by subtracting doors and windows from gross wall area.Window AreaWork out the glass and frame area of windows from width, height and window count.