Construction calculators
Material quantities from dimensions, with the waste allowance shown separately. Quantities are estimates; confirm orders with your engineer or supplier.
Area
Building physics
- Insulation R-Value CalculatorAdd up the thermal resistance of up to three layers from thickness and conductivity (or R per inch), plus surface films, and get the R-value and U-value.
- Heat Loss Through Wall CalculatorCalculate conductive heat loss through a wall, roof or window from its area, U-value or R-value and the temperature difference, plus energy over a period.
- HVAC Cooling Load Estimate CalculatorEstimate a room’s cooling load from conduction, sun through windows, occupants, equipment and outside air, in kW, Btu/h and tons of refrigeration.
Building services
- Cable Tray Fill CalculatorFind the cross-sectional fill of a cable tray from the cable diameters and tray size, compare it with the limit you set and see how many more cables fit.
- Electrical Conduit Fill CalculatorCheck conduit fill from the conduit’s internal diameter and the conductor diameters, against a fill limit you take from your wiring code.
- Plumbing Pipe Flow CalculatorFind the water velocity, friction head loss and pressure drop in a full pipe from the bore, flow rate, length and Hazen–Williams C factor.
- Drainage Slope CalculatorWork out the fall a drain needs for a given gradient, or the gradient from a measured fall, as a percentage, 1 in N, mm per metre and degrees.
- Rainwater Harvesting Tank CalculatorEstimate how much rainwater a roof can collect in a year and size a storage tank to cover your daily demand through the longest dry spell.
- Solar Rooftop Area CalculatorWork out how many solar panels a target system size needs, the roof area they take up, and the largest system that fits on the roof you have.
Carpentry
Carpentry & framing
- Door Frame Material CalculatorWork out the jamb and head cutting lengths for door frames, the total timber length, and how many stock lengths to buy when the cuts are nested.
- Window Frame Length CalculatorWork out the frame, mullion and transom profile lengths for a set of windows and how many stock bars to buy when the cuts are nested.
- Wall Stud Quantity CalculatorCount the studs for a timber or metal stud wall from its length and stud spacing, with extras for openings and corners, plus top and bottom plate lengths.
Carpentry & stairs
- Stair Rise and Run CalculatorFind the number of risers and treads, the exact riser height, total run, stringer length, pitch angle and the 2R + G comfort check for a straight stair.
- Drywall Sheet Count CalculatorCount drywall or plasterboard sheets for a room’s walls and ceiling from its size, openings and sheet size (4×8, 4×12 ft or 1200 mm boards), with waste.
Concrete
- Cement Bags for Concrete CalculatorTurn a concrete volume and a nominal mix such as 1:2:4 into cement bags, sand and coarse aggregate, using a dry-volume factor and your bag size.
- Foundation Concrete CalculatorAdd up the concrete for pad footings and strip (wall) footings in one go, with a waste allowance, in cubic metres, cubic yards and cubic feet.
- Pile Concrete Volume CalculatorEstimate concrete for bored or cast-in-place piles from diameter, length and number, with over-pour above cut-off and an over-consumption allowance.
Cost & productivity
- Labour Productivity CalculatorWork out construction labour productivity as output per labour-hour and labour-hours per unit, and compare it with the rate in your estimate.
- Construction Cost Escalation CalculatorEscalate a construction cost estimate to the midpoint of construction using an annual escalation rate you choose, and see the escalation allowance.
- Construction Retention CalculatorCalculate retention held on an interim valuation, apply an optional limit as a share of the contract sum, and work out the net payment due.
- Contingency Budget CalculatorAdd design and construction contingency percentages to a base cost to get the contingency sum, the total budget and contingency as a share of it.
- Construction Equipment Rental Cost CalculatorFind the cheapest mix of daily, weekly and monthly hire rates for a rental period, then add delivery, damage waiver and sales tax for the total.
- Material Waste Rate CalculatorMeasure construction material waste from quantities delivered, installed and returned, as a share of delivered and as the allowance to add to net quantities.
Earthwork
- Excavation Earthwork CalculatorCalculate excavation volume for a pit or trench with vertical or sloped sides, the loose volume after swell and the number of truckloads to haul it away.
- Site Cut and Fill Volume CalculatorEstimate cut, fill and the net earthwork balance for a site from spot levels on an equal grid, a formation level and a fill shrinkage allowance.
Finishes
- Wall Plastering Quantity CalculatorEstimate cement bags and sand for cement-sand plaster from the wall area, openings, plaster thickness, mix ratio and a dry-volume factor.
- Floor Tile Waste CalculatorWork out how many floor tiles and boxes to buy from the room size, tile size and joint width, with a waste allowance for cuts and breakage.
- Paint Coverage CalculatorEstimate the paint for a room from its size, doors, windows, number of coats and the coverage on the tin, in litres, US gallons and cans.
- Grout Requirement CalculatorEstimate tile grout in kg, lb and bags from the tiled area, tile size, joint width and depth, and grout density, with a waste allowance.
- Waterproofing Area CalculatorCalculate the waterproofing area for a wet room, balcony or roof including wall upturns, and the membrane or coating needed from coverage and coats.
- Ceiling Panel Count CalculatorCount the suspended-ceiling tiles a room needs from its size and the tile size, with a waste allowance, the number of boxes and wall angle lengths.
- Carpet Roll Quantity CalculatorFind the length of carpet to cut from a roll of a given width for a rectangular room, laying strips in whichever direction uses the least carpet.
- Adhesive Coverage CalculatorWork out how much tile, flooring or wall adhesive an area needs from the consumption rate on the datasheet, with waste, and how many packs to buy.
- Wallpaper Roll Count CalculatorCount the wallpaper rolls a room needs from wall width and height, roll size and pattern repeat, using the drops-per-roll method decorators use.
Glazing
Landscaping & external works
Masonry
- Brick Quantity CalculatorCount the bricks for a wall from its length, height, openings, brick size and joint thickness, with mortar volume and a waste allowance.
- Sand Quantity for Mortar CalculatorWork out the sand (volume and weight) and cement bags for a given volume of mortar from the mix ratio, a dry-volume factor and material densities.
Materials estimating
- Roofing CalculatorEstimate the sloped area of a roof from its footprint and pitch, then the roofing squares and shingle bundles to order, with a waste allowance.
- Tile CalculatorWork out how many tiles you need for a floor or wall from its size, the tile size and grout joint, with a waste allowance and boxes to buy.
- Gravel CalculatorEstimate the gravel or crushed stone needed for a driveway, path or base from its size and depth, in cubic metres, cubic yards, tonnes and US tons.
Paving
- Asphalt Road Tonnage CalculatorWork out asphalt tonnage from paved length, width, compacted thickness and mix density, in metric tonnes and US short tons, plus volume and area.
- Paver Block Quantity CalculatorCount paver blocks for a patio, path or driveway from the area, paver size and joint width, with a waste allowance and the bedding sand volume.
Plumbing & water
Reinforcement
- Steel Rebar Weight CalculatorFind reinforcing bar weight from diameter, length and number of bars using steel density, in kg per metre, lb per foot and total kg, lb or tonnes.
- Rebar Spacing CalculatorLay out reinforcing bars across a slab or footing: number of bars for a maximum spacing and end cover, the equal spacing, steel area per metre and total length.
Roofing
Scheduling
- Concrete Curing Time Plan CalculatorTurn a pour date and your specified periods into calendar dates for the end of curing, formwork striking, prop removal and cube or cylinder tests.
- Construction Schedule Float CalculatorCalculate an activity’s total float and free float from its early start, duration, late finish and the earliest start of its successors.
Site setup & temporary works
Structural & reinforcement
- Reinforcement Lap Length CalculatorTurn a lap multiplier from your design code into a lap length, count the laps along a bar run and add the lapped steel length and weight.
- Floor Load Distribution CalculatorDistribute a uniform floor load to joists by tributary width: line load per joist, total load, end reactions and the maximum bending moment of a simple span.