Free tools
DIY tools & calculators
Quick reference charts and calculators for the jobs our guides cover. All metric, all EU-standard, free to use.
Screw & drill-bit size guide
Every DIY guide on this site that involves drilling or screwing references the same sizing standard. Bookmark this page: it saves you a trip to the shed to find your caliper.
Paint coverage calculator
Enter your room dimensions and we'll estimate how many litres of paint you need, how many coats to plan for, and which tin size to buy.
Tile, adhesive & grout calculator
Enter the area you're tiling and the tile size — we'll work out how many tiles, how much adhesive and how much grout to buy.
Concrete & cement calculator
Work out how much concrete you need for a slab, footing, column or post-hole — plus how many 25 kg ready-mix bags, or how much cement, sand and gravel to buy loose.
Plaster & mortar mix calculator
Enter the wall area you're plastering plus type and layer thickness — get the exact kg, 25 kg bags and mixing water needed.
Flooring calculator (laminate / hardwood / vinyl)
Enter your room size and the pack coverage on the flooring box — we'll work out how many packs, underlay rolls and skirting length you need.
Wallpaper calculator
Enter room perimeter and ceiling height, roll size and pattern repeat — we'll work out how many rolls and paste tubs to buy.
Cable size calculator (single- & three-phase)
Switch between single-phase 230 V and three-phase 400 V. Enter the load in watts (or amps), the one-way circuit length and how the cable is installed — we recommend the mm² size, MCB rating and expected voltage drop.
BTU calculator — heating & air conditioning
Switch between heating (radiator) and air-conditioning modes. Enter room dimensions, insulation, windows and orientation — we give required watts, BTU/hr and the nearest standard split A/C size.
Aggregate calculator (gravel / sand / topsoil)
Enter the area to cover and the depth in mm — we work out m³, tonnes and the number of 850 kg bulk bags for gravel, sharp sand or topsoil.
Decking calculator
Enter deck length and width, board width and joist spacing — we work out boards, joists and screws with a safe wastage allowance.
Brick & block calculator
Enter wall length and height, choose brick or block, single or double skin — we work out the count plus mortar volume.
Roof pitch calculator
Enter any two of rise, run or rafter length — we work out the pitch in degrees, the gradient ratio and the missing side.