Home, Energy & DIY
Appliance electricity running costs (kWh), paint room coverage estimators, and flooring box calculators.
Home, energy and DIY calculators work out what a room, a project or an appliance needs before you buy materials or book a tradesperson. They take the measurements you have, in metric or imperial, and turn them into quantities, whole packs or bags, and costs.
The Appliance Running Cost Calculator multiplies an appliance's wattage by the hours it runs and your unit rate, starting from the current Ofgem price cap rate in the UK, and shows the cost per hour, day, month and year. A 2,000W heater on for 3 hours uses 6kWh. Washing machines and dishwashers use presets based on measured energy, because they only draw full power while heating. The BTU Calculator sizes an air conditioner from floor area on the ENERGY STAR chart and converts between BTU per hour, kW and watts.
For decorating, the Paint Calculator takes off about 1.6 m² per door and 1.5 m² per window, allows for the number of coats and adds 10% spare. A 4 m by 3 m room with 2.4 m ceilings needs about 5.6 litres for two coats: one 5 litre tin and one 2.5 litre tin. The Flooring Calculator adds an offcut allowance and rounds up to whole packs, and the Square Footage and Square Metre Calculator measures a single room, an L-shape or a whole house.
For building and garden jobs, the Concrete Calculator, Gravel Calculator, Asphalt Calculator, Cubic Yard Calculator and Cubic Feet Calculator turn area and depth into volume, weight and bags. The Roof Pitch Calculator gives pitch, rafter length and roofing squares, and the Stair Calculator checks risers and treads against Approved Document K in England, the US International Residential Code and Canada's National Building Code.
UK and US units differ in ways that change an order. A US ton is 2,000 lb, a metric tonne is 1,000 kg and a UK long ton is 2,240 lb, and a cubic yard is exactly 27 cubic feet. Each tool shows both systems side by side, but confirm quantities with your supplier before you order.
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Appliance Running Cost Calculator
Work out what any electrical appliance costs to run per hour, day, month and year, starting from the current Ofgem price cap rate.
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Paint Calculator
Work out how much paint you need for a room in litres, with doors and windows taken off and the right mix of 5L and 2.5L tins.
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Flooring Calculator
Work out how much laminate, vinyl, wood or tile flooring you need, how many packs to buy and what it will cost, with an allowance for offcuts.
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Concrete Calculator
Work out how much concrete you need for a slab, footing, post holes or steps in m³ or cubic yards, and how many pre-mixed bags to buy.
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Square Footage and Square Metre Calculator
Work out floor area in square metres, square feet and square yards for one room or a whole house, from metric or feet and inches, with a cost estimate.
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BTU Calculator
Find the air conditioner size a room needs in BTU per hour and kW, using the ENERGY STAR sizing chart, plus a BTU, kW and watts converter.
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Roof Pitch Calculator
Work out roof pitch as x in 12, degrees and percentage, plus rafter length with overhang, roof area in m² and ft², and roofing squares.
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Stair Calculator
Work out risers, treads, riser height, total run, stair angle and stringer length, then check them against UK, US IRC or Canadian stair rules.
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Cubic Yard Calculator
Work out cubic yards and cubic metres of topsoil, mulch, compost, sand or gravel for beds and paths, with bags needed and an optional cost.
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Cubic Feet Calculator
Work out cubic feet for boxes, rooms, fridges and tanks from inches, feet, cm or metres, with cubic metres, litres and US and UK gallons.
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Gravel Calculator
Work out how much gravel, crushed stone or sand you need in cubic yards, m³, US tons and tonnes, with bulk bags and cost, using cited densities.
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Asphalt Calculator
Work out asphalt or tarmac tonnage for a driveway or path from its area and compacted thickness, in US tons and tonnes, with a cost estimate.
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Energy Tariff and Bill Checker
Check if a new energy tariff is cheaper for your usage, find the break-even kWh and exit fee payback, or see exactly why your bill went up.
Common questions about home, energy & diy
How do I work out what an appliance costs to run?
Divide the wattage by 1,000 to get kilowatts, multiply by the hours it runs, then multiply by your unit rate. A 2,000W heater used for 3 hours uses 6kWh, which costs £1.50 at an example rate of 25p per kWh. The Appliance Running Cost Calculator does this per day, month and year.
How much paint do I need for a room?
Measure the wall area, take off doors and windows, multiply by the number of coats and divide by the coverage per litre. The Paint Calculator uses 12 m² per litre by default and adds 10% spare, so a 4 m by 3 m room with 2.4 m ceilings needs about 5.6 litres for two coats.
How much extra flooring should I buy for waste?
Allow 10% for planks laid in straight rows. Herringbone, chevron and diagonal layouts create more angled cuts, so allow 15% or more. A 12 m² room with 10% extra needs 13.2 m², which is 6 packs of 2.2 m². The Flooring Calculator always rounds up to whole packs.
How many bags of concrete make a cubic metre?
About 100 bags of 20 kg Blue Circle Multi-Purpose Concrete, as Tarmac says each bag makes about 0.01 m³. In the US, Quikrete's 80 lb bag makes about 0.60 cubic feet, so a cubic yard takes 45 bags. Yields vary by product, so check the figure printed on your bag.
What size air conditioner do I need for my room?
It depends on floor area. On the ENERGY STAR chart a room of 150 to 250 sq ft needs 6,000 BTU per hour, so a 20 m² bedroom, which is 215.3 sq ft, needs 6,000 BTU/h or 1.76 kW. Add 10% for a very sunny room and 4,000 BTU/h if the unit cools a kitchen.