Construction & DIY Calculators

20 free calculators · Updated for 2026/27

Building and DIY work goes wrong in two familiar ways, by ordering too little material and by underestimating what the finished job costs. Calculators in the building group turn room, wall and roof dimensions into quantities to take to a merchant, and turn project types into cost estimates, which supports deciding whether to do a job yourself, how many bags or packs to buy, and whether an extension or conversion is worth the outlay.

For quantities, the Concrete Calculator says how much concrete a slab, footing or post needs, the Bricks & Blocks Calculator works out bricks, sand and cement for a wall once openings are deducted, and the Flooring Calculator adds wastage before giving pack counts and costs. For the bigger decisions, the Extension Cost Calculator estimates cost per square metre by extension type, and the Staircase Calculator checks risers, treads, pitch and going against Building Regulations Part K.

C

Concrete Calculator

Calculate how much concrete you need in cubic metres or bags for slabs, footings, posts and columns.
P

Paint Calculator — Litres & Coverage

Calculate how much paint you need based on wall area, number of coats and paint coverage rate.
F

Flooring Calculator

Calculate how much laminate, vinyl or carpet you need including wastage. Get pack and cost estimates.
T

Tile Calculator — Tiles Needed & Cost

Calculate how many tiles you need for walls or floors. Accounts for grout gaps and wastage.
G

Gravel Calculator — Tonnes & Cost

Calculate gravel needed in cubic metres, tonnes or bags for driveways, paths and landscaping.
W

Wallpaper Calculator

Calculate how many rolls of wallpaper you need. Accounts for pattern repeat and doors/windows.
D

Decking Calculator — Boards & Cost

Calculate decking boards, joists and screws needed. Get material cost estimates.
F

Fencing Calculator — Panels & Cost

Calculate fence panels and posts needed for your garden fence with material cost estimates.
R

Radiator BTU Calculator

Calculate the BTU and wattage needed for your radiators based on room size, glazing and insulation.
B

Bricks & Blocks Calculator

Calculate bricks, sand and cement needed for walls. Accounts for openings and mortar joints.
I

Insulation Calculator

Compare loft, cavity wall, solid wall and floor insulation costs, savings and payback periods.
R

Roof Tiles Calculator

Calculate roof tiles, ridge tiles, batten and felt needed based on roof dimensions and pitch.
P

Plaster Calculator — Bags & Coverage

Calculate plaster needed in 25kg bags for skim coat, bonding/browning or one-coat plaster.
S

Staircase Calculator

Calculate risers, treads, pitch and going for a staircase. Checks Building Regulations Part K compliance.
L

Loft Conversion Cost Calculator

Estimate loft conversion costs by type (Velux, dormer, hip-to-gable, mansard). See ROI and value added.
E

Extension Cost Calculator

Estimate home extension costs per m² for single/double storey, side return and wrap-around extensions.
B

Bathroom Cost Calculator

Estimate bathroom renovation costs for budget, mid-range and premium finishes with optional extras.
K

Kitchen Cost Calculator

Estimate kitchen installation costs by budget level. Includes units, worktops, appliances and labour.
T

Timber Calculator — Board Feet & Cost

Calculate timber volume, total length and cost for construction projects. Common size presets included.
U

Underfloor Heating Calculator

Compare water, electric mat and cable underfloor heating. See install costs and running costs vs radiators.