Construction & Home
A quantity estimate is only as good as its assumptions about wastage, mix ratio and bulking, so those assumptions are inputs here rather than hidden constants. Where a figure is a convention rather than a measurement (the 1.54 dry-volume factor, for instance) the tool says so and links to where it comes from.
Land
Materials
Concrete Volume CalculatorConcrete volume for a slab, column or footing, with wastage and the ready-mix load count. The dry volume of ingredients is larger than the wet concrete, which is the factor most quantity errors come from.Brick CalculatorBrick count from wall dimensions, with mortar and its cement and sand. Counting the mortar joint as part of each brick is what makes the number come out right.Board Foot / Lumber CalculatorBoard feet for hardwood lumber, which is sold by volume rather than by length. One board foot is 144 cubic inches, and nominal sizes are not actual sizes.
Structural
Roofing Material CalculatorRoofing material from roof area. The number to be careful about is the area itself: a pitched roof is larger than the building footprint by the pitch factor, and using the footprint is the classic underorder.Roof Pitch CalculatorRoof pitch as an angle, a percentage and an area multiplier. The multiplier is the number that matters when ordering material, because a pitched roof is always larger than the footprint beneath it.Staircase Design CalculatorStaircase geometry from the floor-to-floor height. Risers must be equal, so the height decides the count and the count decides the riser, not the other way round.Ramp Slope CalculatorRamp length for a given rise and slope. Accessibility standards cap the rise per flight, so a tall rise needs intermediate landings that add substantially to the total length.Retaining Wall CalculatorBlock count for a segmental retaining wall, counting the buried base course that people forget. Drainage gravel behind the wall matters more than the blocks.
Finishing
Paint Quantity CalculatorPaint quantity from wall area, coverage and coat count. Coverage varies by a factor of two between a smooth sealed wall and fresh plaster, which is why it is an input rather than a constant.Tile CalculatorTile count from floor or wall area, with wastage. Ten percent is the usual allowance and a diagonal or herringbone layout needs more, because every edge cut produces an offcut you cannot use.Tile Grout CalculatorGrout quantity from tile size, joint width and thickness. Smaller tiles need far more grout because there is more joint per square metre.Flooring Cost CalculatorFlooring cost from room dimensions, separating the area to cover from the area to order. Ordering the exact floor area is the standard mistake: every edge cut wastes part of a tile, and a second delivery rarely matches the first batch.Wallpaper CalculatorWallpaper rolls from wall area. A standard roll covers about five square metres in practice rather than the ten it measures, because pattern matching wastes a great deal.Drywall CalculatorPlasterboard sheets from wall or ceiling area. A standard 8 by 4 foot sheet covers about 2.97 square metres, and ten percent wastage is normal for a straightforward room.
Outdoor
Fence CalculatorPosts, rails and pickets for a fence run. The plus-one on posts is the part people miss: a fence with ten sections needs eleven posts, not ten.Asphalt and Driveway CalculatorAsphalt tonnage from area and compacted thickness. Asphalt is dense at around 2,400 kg per cubic metre, so a small area is a surprisingly large delivery.Gravel and Mulch CalculatorGravel or mulch by volume and weight for a given area and depth. Depth is the input that decides everything and fifty millimetres is the usual minimum for coverage.Topsoil CalculatorTopsoil by volume and weight. A lawn wants 100 to 150mm and a planting bed 300 to 450mm, and topsoil settles noticeably after laying.Swimming Pool Volume CalculatorPool volume with a sloping floor, plus the pump flow for a target turnover. A uniformly sloping floor holds exactly what the average depth would, which makes the calculation simpler than it looks.
Plumbing
Electrical
Electrical Load CalculatorHousehold electrical load with a diversity factor. Sizing on connected load rather than diversified load overstates the requirement substantially, because everything is never switched on at once.Wire Gauge CalculatorConductor size from both current capacity and voltage drop. Long runs are limited by drop rather than by current, which is why a cable rated for the load can still be too small.Voltage Drop CalculatorVoltage drop over a cable run. The factor most often missed is that current flows out and back, so the conductor length is twice the run, and long runs fail on drop well before they fail on current rating.Lighting and Lumens CalculatorLighting in lumens from room area and use. Watts measure power consumed and lumens measure light produced, and since LEDs the two have no fixed relationship, so buying by wattage no longer works.
HVAC
Energy
Insulation R-Value CalculatorR value, U value and heat loss for an insulation thickness. Doubling insulation halves the remaining loss, not the original loss, which is why the first 50 mm saves far more than the second.Solar Panel Sizing CalculatorSolar array sizing from daily consumption. Peak sun hours are the equivalent hours at full rated irradiance, not hours of daylight, which is the input people get wrong by a factor of two.Solar ROI and Payback CalculatorSolar payback with the two effects that pull against each other: tariffs rise, which helps, and panels degrade, which does not. Both compound, so a flat saving assumption is wrong within a few years.Generator Sizing CalculatorGenerator sizing with motor starting surge. Sizing on running load alone is the classic error: a motor draws several times its rated power for a second or two on start, and a generator that cannot supply it will stall.
Cost
Construction Cost per Sq Ft CalculatorConstruction cost from built up area and a rate a square foot, with the finish level, contingency and approval fees separated. Roughly half of a house is structure and half is finishing, and it is the finishing half that varies by a factor of three between basic and luxury.Home Renovation Cost CalculatorRenovation cost with bathrooms and the kitchen priced separately from the general area, because wet areas cost several times what a dry room does per square foot and averaging them across the flat hides the real driver.