Mortar Calculator (UK)
Work out the sand and cement for your brickwork or blockwork before you order. This UK mortar calculator sizes the job either way: enter a wall area, or the number of bricks or blocks you're laying, pick your mix ratio, and it returns the mortar volume plus the cement bags and sharp sand you'll need, with wastage built in. It covers standard UK bricks and blocks and the common cement:sand mixes used above and below the damp-proof course. Free, metric, and works on your phone on site.
How to use this mortar calculator
- Measure your wall — enter length × height in metres, or switch to "Enter area" if you already know the m². Alternatively, use "By number of units" if you have a brick or block count from our brick calculator.
- Choose wall type and mix ratio — single-skin brick is the default for most garden walls and house extensions. Pick the mix that matches your exposure (see the table below).
- Read off cement bags and sand — the calculator applies a dry-materials factor of 1.30 to account for compaction, then converts to 25 kg cement bags and bulk sand bags.
- Order with wastage included — the 15% default reflects real-site losses. Bricklayers routinely lose 10–20% of mortar to spillage, droppings and tight boards; 20% is safer on fiddly jobs with lots of cuts and corners.
Mortar mix ratios — which to use
The right mortar mix balances strength, flexibility and breathability. The governing UK standards are BS EN 998-2 (factory-made masonry mortars) and the older BS 5628, which classifies mixes by designation (i) to (v). A critical rule: the mortar should never be stronger than the bricks. Hard mortar locks movement into the units themselves, so thermal or settlement cracks go through the brick face rather than the joint — and repointing a cracked wall costs far more than the cement saved. Modern practice replaces lime with a plasticiser for workability on most jobs, but lime still wins on soft or historic brick where breathability matters.
| Mix (cement : sand) | UK use | Notes |
|---|---|---|
| 1 : 3 | Below DPC, chimneys, copings, retaining walls | Strongest, least flexible |
| 1 : 4 | Exposed façades, parapets, severe weather | Durable general external |
| 1 : 5 | Most house brickwork above DPC | The common all-rounder |
| 1 : 6 | Internal walls, sheltered blockwork | Weaker, more workable |
| 1 : 1 : 6 (cement : lime : sand) | Soft/historic brick, breathable walls | Traditional, self-healing |
Worked example: a 10 m² single-skin garden wall
You're building a 10 m² single-skin garden wall in standard bricks, mix 1:5, 15% wastage.
- Bricks: 10 × 60 = 600 bricks
- Net mortar: 10 × 0.030 = 0.30 m³; +15% = 0.35 m³
- Dry materials (× 1.30): 0.45 m³, split 1:5
- Cement: ≈ 5 × 25 kg bags
- Sharp sand: ≈ 0.6 tonnes (about 1 bulk bag)
At 2026 builders'-merchant prices — roughly £5.50 a 25 kg bag of cement and £52 a bulk bag of sand from Travis Perkins or Jewson — that's around £30 in cement and £52 in sand, call it £85 in materials plus a tub of plasticiser. Scaled up, 1,000 bricks at 1:5 works out to roughly 8 bags of cement and a tonne of sand. Before laying, make sure your foundations are sized — the concrete volume calculator handles the strip footing below.
A point most calculators skip
The biggest mortar mistake isn't the quantity, it's mixing too strong. A 1:3 mix on ordinary facing brick looks reassuringly tough but it's a false economy. Hard mortar can't flex, so movement cracks the bricks rather than the joints, and repointing a cracked wall costs far more than the cement you "saved". Match the mix to the brick, not to your nerves. For the floor finish after the wall is up, the screed calculator and tile calculator handle the next steps.
Frequently asked questions
Related tools
- Brick Calculator UK — work out the brick count before sizing the mortar
- Concrete Volume Calculator — size the foundations and concrete below your wall
- Screed Calculator — sand and cement for floor screeds on the same job
- Tile Calculator — tiles and adhesive for the finish on top
Disclaimer: This calculator gives material estimates for planning only. Actual mortar use varies with joint size, brick type, weather and workmanship. For structural or exposed masonry, confirm the mortar designation against BS EN 998-2 / BS 5628 and your drawings, and consult a qualified professional.