Building and construction
Quantities off a drawing, not off a rule of thumb. Each page takes the dimensions, the mix and the material you specify and returns the volume, the count and the number of bags — with every step of the arithmetic printed so a site engineer can check it against the bar bending schedule or the contractor’s own sheet.
A quantity is arithmetic once three things are known: the space to be filled, how that space is divided up, and what one unit of the material weighs or covers. The dimensions come from the drawing. The rest comes from the specification, and that is why the mix ratio, the brick size, the joint thickness and the coverage are fields on these pages rather than fixed numbers — a site that orders on a default it never checked will pay for a fifth of a wall it does not have.
Only two kinds of value arrive already filled in: a definition, such as the mass a cement bag is sold at or the density of the steel you are counting, and a physical constant. Everything else is yours to enter and yours to have right. A dry-volume factor for concrete, the wastage you allow for breakage, the yield of a paint tin, the lap length a bar needs — these are agreed between a specifier and a supplier, and a general page cannot know which side of the range your project sits on.
The difference between wet and dry volume is the one a first estimate usually misses, so it is stated on the concrete page: the mixed charge occupies more space than the finished wall, because the sand and the aggregate pack around the cement with air still between them. The number the form asks for is the factor for the mix you are actually specifying, taken from the same source as the mix design.
The pages added since then fill in the steps a reader meets before any of those quantities: a flat area in a rectangle, a triangle or a circle; one length in every unit a tape, a drawing and an order form use; the openings a finish has to work around. Sand and gravel are ordered by volume and paid by weight, a roof is bought as sheets at an effective cover, plaster is bought as bags and cubic metres, a pipe is judged by the water it holds, and the two electrical pages add a load and count the points on a wiring estimate.
Where a brief entry would only repeat a page already live on this desk — the square-metre and acre conversions, room area, tile and paint quantities, cement, concrete, brick, steel, the staircase and its risers — the existing page serves it. One address per calculation is the rule on this site, so two pages cannot give two answers, and a reader who arrives from a search engine lands on the page that already carries the arithmetic and its notes.
Every tool in Building and construction
- Cement quantity calculator Bags of cement a volume of concrete needs, from the mix ratio on the drawing and the mass printed on the sack.
- Concrete volume calculator The volume a set of dimensions holds, in cubic metres and in cubic feet, split into the three materials by the mix ratio.
- Brick quantity calculator How many bricks a wall takes, counting the mortar joint into each brick and the openings back out of the wall.
- Steel weight calculator Kilograms of reinforcement from bar diameters and total lengths, using the density of steel rather than a memorised shortcut.
- Tile quantity calculator How many tiles a floor takes, from the tile's own face size and a breakage allowance you set.
- Paint quantity calculator Litres of paint for a room, from the spread rate printed on the can and the number of coats the system asks for.
- Flooring cost calculator What a floor costs laid: material over the area including cuts, and labour on the same area.
- Roof area and slope calculator The developed area of a pitched roof from its plan and its rise, with the slope as a ratio, a percentage and an angle.
- Staircase calculator Risers, treads, the horizontal run a flight takes and the going-and-rise check a code measures, from floor to floor.
- Construction cost estimator A line-by-line estimate sheet: each item's quantity times its rate, a contingency on the total, and a printable summary.
Measuring a space
Area in any shape, one length in every unit and the openings to deduct — measured in the unit your tape is marked in.
- Square feet calculator The area of a rectangle, a triangle or a circle from dimensions you enter, printed in square feet, square metres and square yards — with the unit your tape is marked in kept beside the input.
- Length converter One length in millimetres, centimetres, metres, inches, feet and yards at once, so a measurement taken in one unit can be read, ordered and checked in another.
- Door and window area calculator Add up the clear openings in a room or a wall — every door and window, with how many of each — and get the area to deduct from paint, plaster or brickwork.
Materials and services
Sand, gravel, roofing sheets, plaster and pipe capacity, priced only at the rates you type.
- Sand calculator The volume of a sand bed or fill from its dimensions, with a wastage allowance, and the weight it will show on a weighbridge at the bulk density you enter.
- Gravel calculator The volume of a gravel bed, path or base course from its dimensions, with wastage, and the tonnage at the bulk density you supply.
- Roofing sheet calculator The developed area of a pitched roof and the number of sheets it needs, from the plan size, the slope and the effective cover of one sheet.
- Plastering cost calculator The cement and sand a plaster coat needs from the wall size, thickness and mix, priced at the rates you enter, with labour carried separately so each line can be argued with.
- PVC pipe water capacity calculator How much water a length of pipe holds, from its internal diameter — per metre, per pipe and for the whole run — with the weight that water adds.
Load and wiring
Connected load, the current it implies, the next standard device rating and a point-by-point wiring estimate.
- Electrical load calculator Add up the appliances on a circuit or a connection, apply the diversity you state, and read the current and the next standard supply rating it implies.
- House wiring cost calculator Count the points in a house, put metres of wire against each, and price the run at the wire, labour and accessory rates you enter.