Project guides
How much do I need? DIY materials guides
Plain-English answers to the questions people ask before a trip to the merchant. Each guide gives you the formula, a worked example, a calculator and a full checklist, based on manufacturer guidance.
Indoor jobs
How much paint do I need for a room?Measure the walls, take off doors and windows, multiply by the number of coats and divide by 12. Here is the rule, a worked example and a calculator that does it for you.
How much plasterboard do I need?Each standard 2400 x 1200mm sheet covers 2.88 m². Divide your area by that, add 10% for cuts, then work out the screws, tape and plaster to go with it.
How much plaster do I need to skim a room?A finish skim is about 2mm thick. British Gypsum says a 25kg bag of Multi-Finish covers about 10 m² at that thickness.
Stud wall materials list: what do I need?A timber stud partition is CLS studs at 400mm centres between a head and sole plate, boarded both sides. Here is everything on the list and how much of each.
How many tiles do I need, and how much adhesive and grout?Work out the area, divide by the size of one tile and add 10% for cuts. Adhesive and grout depend on where you are tiling and the joint size.
How much loft insulation do I need for 270mm?The Energy Saving Trust recommends 270mm of mineral wool in a loft. Here is how many rolls that takes, from scratch or as a top-up.
Garden and outdoor jobs
How many fence panels and posts do I need?Divide the length of the run by the panel width and round up. You need one more post than panels, plus one for each corner or gate.
How many feather-edge boards for a closeboard fence?A closeboard fence is built on site from posts, arris rails and overlapping feather-edge boards. The overlap is what most lists get wrong.
How much decking do I need?Boards are the easy part. The frame underneath is where most DIY lists go wrong, so this guide follows the Timber Decking & Cladding Association (TDCA) handbook.
How much concrete do I need for a shed base?Make the base a little bigger than the shed, work out the volume, and convert it to bags of cement and ballast for a 1:5 mix.
How much sand and cement do I need for bricks, blocks or slabs?Work out the volume of mortar first, then split it into cement and sand by the mix. Here are the standard UK rates for brickwork, blockwork and laying paving slabs.
How we work out quantities
Every guide uses the same formulas as the SmartBuild app, with coverage figures from manufacturers' data sheets (British Gypsum, Knauf, Dulux, Heidelberg Materials, Marshalls and others) and the Timber Decking & Cladding Association. Each page lists its sources. We add a sensible allowance for cuts and waste and round up to whole packs, and we never write prices into the guides: the app prices your list from live supplier feeds.
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