Free Construction and Trades Calculators
Free UK construction and trades calculators built to be genuinely useful for roofers, builders, electricians and serious DIYers. New tools added regularly, all focused on UK standards and metric units.
Browse by category to find roofing, concrete, electrical and timber calculators for UK projects.
42 tools
Concrete & screed
Customisable
Concrete Slab Bag Calculator
Calculate how many bags of concrete you need for a slab based on size, thickness, and bag weight.
Concrete & screed
Free
Dry Pour Concrete Calculator
Calculate dry pour concrete volume and bags needed for a slab with metric and imperial support.
Concrete & screed
Free
2 Inch Concrete Slab Calculator
Calculate concrete volume and bags needed for a 2-inch thick slab with metric and imperial support.
Concrete & screed
Free
Weight of Concrete Slab Calculator
Calculate the weight of a concrete slab in kg, tonnes and lb from length, width and thickness.
Groundworks & surfacing
Free
Gravel Under Concrete Slab Calculator
Calculate sub-base gravel volume, tonnes and bulk bags for a concrete slab.
Groundworks & surfacing
Free
UK Gravel Calculator
Work out how much gravel you need in m³, tonnes and bulk bags for driveways, paths and borders. Uses UK densities and bag sizes.
Groundworks & surfacing
Free
Paving Calculator UK
Work out how many block pavers or paving slabs you need, plus bedding sand and cost, from your patio or driveway size. Covers standard UK sizes with wastage allowance.
Groundworks & surfacing
Free
Tarmac Calculator UK
Free UK tarmac calculator. Work out how many tonnes of tarmac — or bags of cold-lay — you need for a driveway, path or car park, plus coverage per tonne and optional cost.
Groundworks & surfacing
Free
Fencing Cost Calculator UK
Work out fencing cost in the UK: panels or featheredge boards, posts, gravel boards, concrete and a total price with cost per metre. Covers panel and closeboard modes with editable 2026 prices.
Building Fabric
Free
Dew Point Calculator UK
Get the dew point from temperature and humidity, then check any wall, roof or floor for surface condensation and mould risk. BS EN ISO 13788.
Building Fabric
Free
U-Value Calculator UK
Build your wall, roof or floor layer by layer to get the U-value in W/m²K, with an Approved Document L compliance check. Metric, BS EN ISO 6946 method.
Concrete & screed
Free
Monolithic Concrete Slab Calculator
Calculate concrete volume for a monolithic slab (slab-on-grade) including thickened edges.
Concrete & screed
Customisable
Concrete Footing Calculator
Estimate concrete volume for trench footings, pad footings, and round post holes — plus bags and cost.
Concrete & screed
Customisable
Concrete Volume Calculator
Calculate concrete volume for slabs, footings, and columns with metric and imperial support and bag estimator.
Concrete & screed
Free
Rebar Weight Calculator
Calculate rebar weight per metre, total weight, and tonnes with diameter and length.
Roof & tiling
Free
Roof Pitch Calculator
Convert rise and run into pitch ratio, degrees, and slope instantly with metric and imperial support.
Roof & tiling
Free
Roof Tile Calculator
Work out gauge, tiles per m² and total tiles for plain, interlocking, pantile and slate roofs.
Roof & tiling
Free
Roof Batten Spacing Calculator (UK)
Calculate correct roof batten spacing based on tile gauge, roof pitch and tile type.
Roof & tiling
Free
Rafter Length Calculator (UK)
Calculate rafter length using pitch, roof span/run, overhang, and optional birdsmouth allowance. Metric-first.
Roof & tiling
Free
Brick Calculator UK
Work out how many bricks you need for a wall, with mortar joints and waste included.
Concrete & screed
Free
Concrete Truck Load Calculator
Convert concrete volume into estimated ready-mix truck loads. Choose truck sizes, add wastage, and see loads plus remainder.
Timber & framing
Free
Deck Stair Stringer Calculator
Calculate deck stair steps, rise/run and stringer length for 2×10 or 2×12. Metric & imperial.
Roof & tiling
Customisable
Tile Calculator
Calculate how many tiles you need for floors, walls, showers or bathrooms. Supports m², sq ft, cm & mm.
Concrete & screed
Free
Mortar Calculator
Free UK mortar calculator. Work out sand, cement and mortar for brickwork and blockwork by wall area or brick count, with mix ratios and wastage.
Timber & framing
Free
Stud Wall Calculator UK
Work out how many studs, plates, noggins and plasterboard sheets you need for a timber partition wall. Metric, UK CLS sizes, 400mm or 600mm centres.
Interiors & finishing
Free
Wallpaper Calculator UK
Work out how many rolls of wallpaper you need using the drop-counting method, with pattern repeat, match type and wastage. Metric, standard 10.05m × 0.53m rolls.
Interiors & finishing
Free
Paint Coverage Calculator (UK)
Free UK paint coverage calculator. Work out how many litres of paint you need for walls and ceilings with real-world coverage rates, tin recommendations and mist coat for new plaster.
Timber & framing
Free
Floor Joist Span Calculator UK
Find the maximum clear span for C16 or C24 floor joists at 400–600 mm centres, or the joist size you need for a given span.
Timber & framing
Free
Staircase Calculator (UK)
Work out the number of steps, individual rise, going and pitch for a domestic staircase to Approved Document K, with pass/fail compliance checks and stringer length.
Cost estimators
Free
Extension Cost Calculator UK
Estimate the cost of a single-storey, double-storey or wrap-around house extension with 2026 UK regional rates, cost per m², kitchen, glazing, underfloor heating and professional fees.
Concrete & screed
Free
Screed Calculator
Work out sand, cement and liquid screed for any floor area and depth, with mix ratios, wastage and material costs.
Timber & framing
Free
Timber Calculator UK
Work out how many stock lengths to buy, total volume in m³, offcut waste and estimated cost for any timber section. Supports all common UK carcassing and CLS sizes.
Timber & framing
Free
Decking Area Calculator
Quickly calculate the area of your decking project in square metres or square feet, including waste allowance for both rectangular and circular decks.
Timber & framing
Free
Plasterboard Calculator UK
Free UK plasterboard calculator. Work out how many sheets you need for walls, ceilings or a whole room, in metric, with a waste allowance and standard UK board sizes.
Electrical (BS 7671)
Free
Voltage Drop Calculator
Fast voltage drop calculator for DC, single-phase AC, and three-phase AC. Supports copper/aluminium, metric mm² and AWG/kcmil, power loss, and auto cable sizing.
Cost estimators
Customisable
Landscape Services Estimate Template
Generate professional landscaping quotes with editable unit prices, service quantities, subtotal, tax, and total. Export to CSV or print.
Cost estimators
Free
CIS Tax Deduction Calculator UK
Work out CIS deductions at 20% or 30% on the labour element of a subcontractor invoice, with materials excluded. Free UK calculator with 2026/27 rates.
Electrical (BS 7671)
Free
Cable Sizing Calculator UK (BS 7671)
Free UK cable sizing calculator to BS 7671. Work out cable size, current-carrying capacity and voltage drop for twin & earth and SWA cables up to 50mm².
Groundworks & surfacing
Free
Topsoil Calculator UK
Work out how much topsoil you need in cubic metres, litres, tonnes and bulk bags from your area and depth, with a wastage allowance.
Cost estimators
Free
Loft Conversion Cost Calculator UK
Estimate the cost of a dormer, hip-to-gable, mansard or rooflight loft conversion by floor area, region and finish, with 2026 UK build rates and professional fees.
Cost estimators
Free
Roof Cost Calculator UK
Estimate the cost of a new roof or full re-roof — concrete tiles, clay, natural slate or a flat roof — with scaffolding, waste, region and complexity factored in. 2026 UK rates.