Gravel and Aggregate Calculator UK: Tonnes, m² and Bulk Bags
Typical UK planning depths. Your designer or supplier may specify more.
The calculator inserts a typical planning density. Replace it with the bulk density stated by your quarry or builders' merchant for a more accurate estimate.
Enter a valid density greater than zero.
Enter a measurement greater than zero.
Enter a measurement greater than zero.
Enter a measurement greater than zero.
Enter a measurement greater than zero.
Enter a measurement greater than zero.
Enter a depth greater than zero.
This uplift covers normal variation, spillage and compaction. Set it to 0 if your supplier or specification already includes an allowance.
Allowance cannot be negative.
Enter a bag weight greater than zero.
Enter a bag weight greater than zero.
Delivery, minimum-order and access charges are not included.
Enter a cost greater than zero.
Estimated aggregate requirements
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Check the supplier's product density, moisture condition and actual bag weight before ordering. For structural or adopted-highway work, use the project specification and professional design rather than a general online estimate.
Pick a project or a material, then enter the area and depth. This gravel calculator works out cubic metres, tonnes, bulk bags and the area each tonne covers. It handles gravel, MOT Type 1, sand and topsoil.
More free UK building calculators
Aggregate usually goes down first. These calculators cover the concrete, surfacing and walls that follow.
Cubic metres, bags, cement and ballast for slabs and footings.
Tonnage, coverage and driveway cost per m².
Bricks per m², mortar and cost for any wall.
Slabs, block paving, sub-base, bedding mortar and patio fall.
MOT Type 1 tonnes, bulk bags, layers and dig-out depth.
Concrete, paving, grid or timber shed bases, with dig depth and cost.
Sharp, building and kiln-dried sand, plus sand and cement mixes.
Concrete, breeze and aircrete blocks, with mortar and cost.
Why gravel orders so often come up short
Consider a typical weekend project. Eight bulk bags of MOT Type 1 sit on the drive, and you booked the digger for one day. By lunchtime, the plate compactor has consolidated the stone, and a third of the area remains bare.
Stone settles considerably when you compact it. Most people measure the finished depth, then order loose stone by volume. That difference can mean a second delivery charge and an expensive wasted day of plant hire.
Gravel behaves similarly on a smaller scale. A thin top layer looks patchy, so people purchase additional bags individually. So how do you get the order right first time?
The simple fix: measure the finished compacted depth, use a realistic density, then add 10% for compaction and spillage. The aggregate calculator above does all three for you.
How much area does a tonne of gravel cover?
A tonne of 20 mm gravel covers about 11.8 m² at 50 mm deep. The same weight of 10 mm pea gravel covers about 15.6 m² at 40 mm.
How much MOT Type 1 do I need per m²?
A patio sub-base at 100 mm needs about 0.2 tonnes per m², so one tonne covers 5 m². A driveway at 150 mm needs 0.3 tonnes per m².
How to use the gravel calculator
Our gravel calculator takes less than a minute, and the project presets handle most of the work.
- Choose the shape. Select a rectangle, an L-shape or a circle. Divide irregular areas into two rectangles.
- Pick a project. Presets automatically fill in the material and a typical UK depth, from patios to gravel driveways.
- Check the material and density. Change either one, or enter the density specified by your supplier.
- Enter the area and depth. Use metres and millimetres, or switch to feet and inches.
- Set the allowance and bag sizes. Most merchants sell bulk bags of 800–1,000 kg and small bags of 20–25 kg.
- Add a price if required. Then download or share the estimate as an image.
Gravel calculator formula: how to work out tonnes
Every aggregate estimate follows the same four calculations. You only need the area, the depth and the material density. The same method gives the quantity and amount needed for 10mm or 20mm gravel.
Coverage per tonne and per bulk bag
| Material | Depth | One tonne covers | One 850 kg bag covers |
|---|---|---|---|
| MOT Type 1 | 75 mm | 6.7 m² | 5.7 m² |
| MOT Type 1 | 100 mm | 5.0 m² | 4.3 m² |
| MOT Type 1 | 150 mm | 3.3 m² | 2.8 m² |
| 20 mm gravel | 50 mm | 11.8 m² | 10.0 m² |
| 10 mm pea gravel | 40 mm | 15.6 m² | 13.3 m² |
| 40 mm slate chippings | 50 mm | 14.3 m² | 12.1 m² |
| Sharp sand | 40 mm | 15.6 m² | 13.3 m² |
| Screened topsoil | 100 mm | 8.3 m² | 7.1 m² |
Before the ordering allowance. Calculated with the tool on this page using its planning densities.
Gravel and aggregate calculator examples for UK projects
We ran each project through the calculator using a 10% allowance and standard 850 kg bulk bags.
Case study 1: gravel driveway
A 10 × 3 m driveway: 150 mm of MOT Type 1, topped with 50 mm of 20 mm gravel
Prefer a sealed surface? Compare the cost with our tarmac calculator.
Case study 2: patio sub-base and sand bed
A 4 × 3 m patio with 100 mm of MOT Type 1 and a 40 mm sharp sand bed
Case study 3: round pea gravel feature
A circle 3 m across, filled with 10 mm pea gravel at 40 mm deep
Here is our honest opinion. Twenty small bags usually cost more than one bulk bag, and they mean twenty separate lifts. Small bags only win when deliveries cannot reach the garden.
Case study 4: shed base
A 3 × 2.4 m shed base with 100 mm of MOT Type 1
Aggregate calculator: converting m³ to tonnes
Merchants sell aggregate by weight, but you measure the project by volume. Density connects the two measurements. Multiply cubic metres by the density to get tonnes.
| Material | Planning density | 1 m³ weighs |
|---|---|---|
| MOT Type 1 | 2.0 t/m³ | 2.0 tonnes |
| 20 mm gravel | 1.7 t/m³ | 1.7 tonnes |
| 10 mm pea gravel | 1.6 t/m³ | 1.6 tonnes |
| Sharp sand | 1.6 t/m³ | 1.6 tonnes |
| 20 mm all-in ballast | 1.9 t/m³ | 1.9 tonnes |
| Screened topsoil | 1.2 t/m³ | 1.2 tonnes |
Typical planning densities. Wet sand and soil weigh noticeably more.
Moisture creates the biggest variation. A wet bulk bag of sand can weigh considerably more than a dry one. Yet it holds exactly the same volume. Always use the density published by your quarry or merchant whenever available. For sharp, building or kiln-dried sand, our sand calculator covers every type.
Which gravel should I use, and how deep?
Stone size affects both the appearance and the depth you need. Smaller stones need a thinner layer, while larger stones need additional depth to hide the base. Choose the stone first, then enter the depth in the gravel calculator.
| Gravel | Typical depth | Best for |
|---|---|---|
| 10 mm pea gravel | 30–40 mm | Paths and play areas, but it moves underfoot |
| 20 mm gravel | 40–50 mm | Driveways and borders, because it locks together better |
| 40 mm slate or cobbles | 50 mm | Decorative borders, not walkways |
| Self-binding gravel | 50–75 mm, compacted | Firm paths that still look natural |
| Gravel grids | Fill the cells plus a thin top layer | Driveways where stones must stay put |
For driveways, we prefer 20 mm angular gravel over pea gravel. Rounded pea gravel rolls under tyres and spreads onto the pavement. Gravel driveways are also usually permeable, which matters in front gardens. The government explains the rules in its guidance on permeable front gardens.
How much MOT Type 1 do I need?
MOT Type 1 contains crushed stone sized from 40 mm down to dust. The fines fill the gaps, so it compacts into a firm, load-bearing layer. That makes it the standard UK sub-base beneath patios, paths and driveways. Our sub-base calculator also works out the layers and dig depth.
- Paths and patios: 75–100 mm of compacted MOT Type 1.
- Car driveways: about 150 mm, or more on soft clay.
- Shed and garden building bases: about 100 mm.
Compact it in layers of no more than approximately 75 mm, using a plate compactor. Recycled Type 1 and Type 3 suit certain projects too, so check your design first. Our MOT Type 1 depth and compaction guide explains layers, membranes and Type 3 in detail.
Planning a concrete patio instead? Read our guide on whether a concrete patio needs a permit. Building a garden wall alongside it? Count the bricks with our brick calculator.
Gravel and aggregate prices in 2026
We checked UK merchant listings and trade price guides in October 2026. Prices vary considerably by region and delivery distance.
| Material | Typical price (2026) | Notes |
|---|---|---|
| MOT Type 1, bulk bag | about £44–£80 inc. VAT | Granite costs more than limestone |
| Sharp sand, bulk bag | about £42–£75 inc. VAT | Builders merchants vary widely |
| 10 mm pea gravel, bulk bag | about £70–£90 | Decorative colours cost more |
| 20 mm gravel, loose load | about £32–£48 per tonne ex. VAT | Bulk bags cost 25–40% more per tonne |
Delivery is often extra. Always confirm the bag weight, because 800 kg and 1 tonne bags look the same.
Above roughly 8–10 tonnes, a loose tipper load usually beats bulk bags on price. Below that, bulk bags are considerably easier to handle and store. Enter your own price per tonne in the aggregate calculator for a precise total.
Gravel ordering mistakes to avoid
Our perspective changed while developing this calculator. We expected incorrect areas to cause most problems. In reality, incorrect depths and densities cause equally many.
- Ignoring compaction. Sub-base settles noticeably, so allow at least 10% extra.
- Guessing the depth. Measure several locations, because ground is rarely level.
- Assuming every bag weighs a tonne. Many bulk bags hold 800–850 kg.
- Skipping the membrane. A weed membrane under decorative gravel stops it sinking into soil.
- Buying small bags for big projects. Each 25 kg bag costs considerably more per tonne.
- Lifting excessive weight. Shovel from bulk bags instead of carrying them.
Shifting tonnes of stone manually is genuinely exhausting work. HSE explains safe lifting in its manual handling guidance.
Gravel calculator FAQs
How our gravel calculator turns m³ into tonnes
The calculator converts your measurements to metres and calculates the area and volume. It multiplies the volume by the material density, adds your allowance, then rounds up to whole bags.
The densities are typical UK planning figures, and you can replace any of them individually. Every case study on this page came straight from the calculator. Prices reflect UK listings checked in October 2026.
Back to those eight bulk bags and the bare patch at lunchtime. Measuring the compacted depth and adding 10% prevents the problem entirely. Prices and densities checked in October 2026. Treat results as estimates and confirm densities with your supplier.
Which project are you planning, and which stone have you chosen? Tell us through our contact page. Real projects help us improve its accuracy.