How this is worked out
Blocks per m² is 1 ÷ (block length × block width) in metres, which gives 50 for a 200 × 100mm block. We multiply by your area and add the cuts allowance.
Sub-base and sand are area × depth, which gives cubic metres. To turn that into tonnes we assume compacted MOT Type 1 weighs about 2.1 tonnes per m³ and sharp sand about 1.6 tonnes per m³. Merchants’ figures vary a little, so ask yours what a bulk bag of each covers.
The depths default to Marshalls’ guidance for domestic driveways: 150mm of sub-base and a 30mm compacted laying course.
Worked example
A 6m × 4m driveway is 24 m². At 50 blocks per m² that’s 1,200 blocks, or 1,260 with 5% for cuts.
Sub-base: 24 × 0.15 = 3.6 m³, about 7.6 tonnes of Type 1. Sand: 24 × 0.03 = 0.72 m³, about 1.2 tonnes.
Before you order
- Dig out enough for the sub-base, the sand and the block thickness, usually 50 or 60mm for driveway blocks. On a drive that’s often around 240mm in total.
- Plan a fall of about 1 in 80 away from the house so water runs off, and check the finished level stays at least 150mm below the damp-proof course.
- In England, a new or replacement front garden surface over 5 m² needs planning permission unless it’s permeable or drains to a lawn or border. Check your council’s rules if you’re in Wales, Scotland or Northern Ireland.
What this doesn’t cover
Kiln-dried jointing sand, membrane, kerbs and drainage channels are extra. The calculator also assumes a simple stretcher or herringbone layout on a flat area; a sloped site or one with steps needs measuring section by section.
Questions people ask
How many block paviors are there in a square metre?
Standard 200 × 100mm blocks come to 50 per m². Other sizes work out differently, so enter your block size and the calculator does the sum.
How deep should the sub-base be for a driveway?
Marshalls says 150mm of compacted sub-base should be enough for most domestic driveways. Soft or clay ground may need more, and a patio that only takes foot traffic often uses about 100mm.
How much sand goes under block paving?
Marshalls gives a compacted laying course of 30mm, and never more than 40mm. Lay it loose a bit deeper so it compacts down to that.
How much extra should I allow for cuts?
About 5% for a simple rectangle. Go to 7 to 10% for curves, lots of manhole covers or a herringbone pattern laid at 45°.
Sources
Trade review pending. A named tradesperson will check this calculator, and their name and qualifications will appear here.
Figures last checked 25 October 2026. Read how we calculate and our disclaimer. Found a mistake? Tell us.