Overview
A single deep gravel layer without a sub-base rutts and migrates — the layers, not total depth, make the drive.
How the calculation works
Sub-base tonnes = driveway area × compacted sub-base depth × 2.2 t/m³ (Type 1), plus compaction allowance when ordering loose.
Surface tonnes = same area × gravel dressing depth (40-50mm) × 1.6 t/m³.
A 50 m² drive at 125mm Type 1 plus 50mm gravel needs roughly 13.75 t of sub-base and 4 t of gravel before allowances.
Worked example
Driveway 10m × 5m (50 m²): 125mm MOT Type 1 sub-base plus 40mm of 20mm gravel.
Sub-base: 50 × 0.125 × 2.2 = 13.75 tonnes; with 10% allowance order 15.1 tonnes.
Gravel: 50 × 0.04 × 1.6 = 3.2 tonnes; with a 10% allowance, order about 3.5 tonnes.
MOT Type 1 at a glance
- Planning density2.20 t/m³
- Typical range2.00–2.30 t/m³
- CategorySub Base
- CompactionOften relevant
- SourcePlanning midpoint of published UK supplier data (≈2.0–2.3 t/m³ range observed)
- Reviewed2026-08-16
Planning values for typical UK supplies; your supplier product data takes precedence.
MOT Type 1 coverage guide
| Depth | Area per tonne | Area per 850kg bag | Weight per m² |
|---|---|---|---|
| 25mm | 18.2 m² | 15.5 m² | 55 kg |
| 40mm | 11.4 m² | 9.7 m² | 88 kg |
| 50mm | 9.1 m² | 7.7 m² | 110 kg |
| 75mm | 6.1 m² | 5.2 m² | 165 kg |
| 100mm | 4.5 m² | 3.9 m² | 220 kg |
| 150mm | 3.0 m² | 2.6 m² | 330 kg |
Computed from a 2.20 t/m³ planning density on level ground.
Assumptions and accuracy
Sub-base depth is a design decision based on subgrade and use; 100-150mm is common for private cars, not a universal rule.
Check the specification required for your project and confirm quantities with your contractor or material supplier.
Edging, membrane and drainage are separate materials not included in the tonnage.
Planning density values
Use supplier product data whenever available. These figures are planning defaults shared by every calculator on the site.
| Material | Category | Planning density | Typical range | Compaction |
|---|---|---|---|---|
| MOT Type 1 | Sub Base | 2.20 t/m³ | 2.00–2.30 t/m³ | Relevant |
| MOT Type 3 | Sub Base | 2.10 t/m³ | 1.90–2.20 t/m³ | Relevant |
| Recycled Type 1 | Recycled | 2.00 t/m³ | 1.80–2.20 t/m³ | Relevant |
| 6F2 / 6F5 crushed aggregate | Recycled | 2.00 t/m³ | 1.80–2.20 t/m³ | Relevant |
| Road planings | Recycled | 2.00 t/m³ | 1.80–2.20 t/m³ | Relevant |
| Sharp sand | Sand | 1.60 t/m³ | 1.50–1.70 t/m³ | Usually no |
| Building sand | Sand | 1.50 t/m³ | 1.40–1.60 t/m³ | Usually no |
| Kiln-dried sand | Sand | 1.50 t/m³ | 1.40–1.60 t/m³ | Usually no |
| 10mm pea shingle | Gravel | 1.60 t/m³ | 1.40–1.70 t/m³ | Usually no |
| 20mm gravel / shingle | Gravel | 1.60 t/m³ | 1.40–1.70 t/m³ | Usually no |
| Decorative gravel | Decorative | 1.50 t/m³ | 1.30–1.70 t/m³ | Usually no |
| Slate chippings | Decorative | 1.60 t/m³ | 1.40–1.80 t/m³ | Usually no |
| Gabion stone | Gravel | 1.50 t/m³ | 1.40–1.60 t/m³ | Usually no |
| Self-binding gravel | Gravel | 1.90 t/m³ | 1.80–2.10 t/m³ | Relevant |
| Crushed concrete | Recycled | 1.90 t/m³ | 1.70–2.10 t/m³ | Relevant |
| Limestone scalpings | Sub Base | 2.00 t/m³ | 1.80–2.20 t/m³ | Relevant |
| Ballast | Sand | 1.70 t/m³ | 1.60–1.80 t/m³ | Usually no |
| Generic aggregate | General | 1.70 t/m³ | 1.50–2.20 t/m³ | Usually no |
Typical depth guidance by project type
| Project type | Common depth range | Typical materials |
|---|---|---|
| Driveway | 100–150mm compacted | MOT Type 1, Recycled Type 1, 6F2 / 6F5 crushed aggregate |
| Garden path | 50–100mm compacted | 20mm gravel / shingle, Self-binding gravel, Decorative gravel |
| Patio sub-base | 75–100mm compacted | MOT Type 1, Recycled Type 1, Sharp sand |
| Decorative border | 40–50mm compacted | Decorative gravel, Slate chippings, 10mm pea shingle |
| Shed base | 75–100mm compacted | MOT Type 1, Limestone scalpings, Ballast |
| Drainage layer | 50–150mm compacted | 10mm pea shingle, 20mm gravel / shingle |
| General fill | 100–300mm compacted | 6F2 / 6F5 crushed aggregate, Crushed concrete, Generic aggregate |
Common planning ranges only; ground conditions and loads can require a different specification.
How to use this calculator
- Measure the full driveway area including any turning spaces.
- First run: select MOT Type 1 and enter the sub-base depth; note the tonnage.
- Second run: select 20mm gravel and enter 40-50mm; note the tonnage.
- Add both totals with their allowances for the complete order.
When a gravel driveway is commonly used
Gravel driveways on firm subgrade with secure edging; the same two-layer method sizes parking bays, hardstandings and gravel paths for foot traffic (with shallower layers).
Frequently asked questions
How much gravel do I need for a driveway?
For the surface dressing allow 64-80kg per m² (40-50mm of gravel). The sub-base beneath is a bigger order: 220-275kg of Type 1 per m² at 100-150mm compacted.
What gravel is best for a driveway?
A 20mm angular gravel knits and resists scatter; avoid 10mm pea shingle on turning areas. Angular gravel over a Type 1 sub-base is the standard combination.
How deep should a gravel driveway sub-base be?
Private driveways commonly use 100-150mm of compacted Type 1, but soft ground or heavier vehicles can require more. This is an engineering decision for your specific site.
How do I stop gravel migrating off the driveway?
Run continuous edging or kerbs flush with the surface, keep the gravel dressing to 40–50mm, and use a 20mm angular gravel — it knits together, while rounded pea gravel rolls and spreads.
References and source notes
- Standards for Highways — current Specification for Highway Works (MCHW, restructured September 2025; granular sub-base formerly under Series 800) (sub-base context) — standardsforhighways.co.uk
- Driveway layer guidance summarised from UK trade practice; confirm depths for your site with a contractor.