Gravel Calculator - Volume, Tonnage and Cost
Get the exact volume and tonnage of gravel, crushed stone or aggregate for any driveway, path, patio base, drainage, garden bed or decorative surface. Includes sub-base layers, bag counts, bulk bag options and cost - all from real landscape formulas.
Advanced options
Total Gravel Needed
Material Breakdown
| Layer | Volume | Weight | Notes |
|---|
Ordering Options
| How to buy | Quantity |
|---|
How to Use Gravel Calculator for Driveways, Paths, Patios and Garden Beds Calculations
Pick your surface type, enter the dimensions, choose gravel type and depth, and the calculator returns volume, weight, bag count and cost.
Recommended Gravel Depth by Application
Getting the depth right matters more than the type of gravel. These are the industry-standard depths for every common use.
| Application | Depth | Sub-base needed? | Notes |
|---|---|---|---|
| Decorative garden mulch | 40 - 50 mm | No | Weed membrane recommended |
| Footpath / walkway | 50 mm | Optional 75 mm | Compact surface |
| Patio base | 50 mm | Yes - 100 mm | Bedding layer for slabs |
| Driveway - light use | 50 - 75 mm top | Yes - 100 - 150 mm | Cars only |
| Driveway - heavy use | 75 - 100 mm top | Yes - 200 mm | Vans, trucks |
| French drain | 150 mm | No | Surround perforated pipe |
| Soakaway | 300 - 500 mm | No | Lined pit filled with gravel |
| Playground safety | 300 mm | No | EN 1177 certified gravel |
| Parking area | 100 mm | Yes - 150 mm | Grid system recommended |
| Raised bed top layer | 50 mm | No | Drainage layer |
Gravel and Aggregate Densities
Every gravel type has a different density, which affects the weight you need to order. These are the standards the calculator uses.
| Type | Density (kg/m³) | Density (lb/ft³) | Best for |
|---|---|---|---|
| Pea gravel | 1,500 | 94 | Paths, borders, decorative |
| Crushed stone 20 mm | 1,600 | 100 | Driveways, drainage |
| Decomposed granite | 1,650 | 103 | Paths, patios, compactable |
| River rock | 1,550 | 97 | Decorative, water features |
| Limestone chips | 1,600 | 100 | Garden borders, paths |
| Slate chips | 1,500 | 94 | Decorative mulch, borders |
| Marble chips | 1,500 | 94 | Premium decorative finish |
| Basalt | 1,700 | 106 | Driveways, heavy use |
| Crusher run (MOT Type 1) | 1,700 | 106 | Sub-base, compacted |
| Sharp sand | 1,600 | 100 | Bedding, paving joints |
How Far Does a Bulk Bag or Tonne of Gravel Go?
Quick reference for planning your order. Coverage assumes a uniform spread at the stated depth.
| Depth | Per tonne (pea gravel) | Per 850 kg bulk bag | Per m³ |
|---|---|---|---|
| 25 mm | 26 m² | 23 m² | 40 m² |
| 40 mm | 16 m² | 14 m² | 25 m² |
| 50 mm | 13 m² | 11 m² | 20 m² |
| 75 mm | 8.8 m² | 7.5 m² | 13.3 m² |
| 100 mm | 6.6 m² | 5.6 m² | 10 m² |
| 150 mm | 4.4 m² | 3.7 m² | 6.6 m² |
How the Gravel Calculator Works
Every result uses the standard landscape materials estimation method. Here is the exact process.
- Area is calculated from your dimensions or entered directly.
- Volume = area × depth. Depth is converted to metres (or feet) first.
- Weight = volume × gravel density. Each gravel type has its own density.
- Sub-base, if selected, is calculated as a separate layer with MOT Type 1 density.
- Wastage is added as a percentage on top so you always have spare material.
- Bag counts are computed from your chosen packaging - bulk bag, 25 kg, or 20 kg.
- Cost = total weight (or bags) × your price per unit.
Gravel Formula and Worked Example
These are the exact formulas used by the calculator. Bookmark this section if you want to verify the numbers yourself.
- Area = length × width
- Volume (m³) = area × depth (in metres)
- Weight (kg) = volume × density
- Tonnage = weight ÷ 1,000
- Bulk bags = ceil(weight ÷ 850)
- 25 kg bags = ceil(weight ÷ 25)
- Cost = weight × price per tonne (or bags × price per bag)
Worked example: A 10 m × 3 m driveway with 75 mm top layer of pea gravel. Area = 30 m². Volume = 30 × 0.075 = 2.25 m³. Weight = 2.25 × 1,500 = 3,375 kg = 3.4 tonnes. With 10% wastage = 3.7 tonnes. If bought in 850 kg bulk bags, that is 5 bags. At $50 per tonne, cost = 3.7 × 50 = $185.
Frequently Asked Questions About Gravel Calculation
How much gravel do I need for a driveway?
For a standard driveway, use a depth of 50 - 75 mm of decorative gravel on top of a 100 - 150 mm compacted MOT Type 1 sub-base. For a 30 m² driveway, that means about 1.5 m³ of top gravel and 3 - 4.5 m³ of sub-base. The calculator handles both layers when you select the sub-base option.
How many tonnes of gravel in 1 m³?
It depends on the gravel type. Pea gravel is about 1.5 tonnes per m³, crushed stone is 1.6 tonnes, decomposed granite is 1.65 tonnes, and crusher run is 1.7 tonnes. The heavier the stone, the more tonnes per cubic metre. The calculator uses the correct density for the gravel type you select.
How deep should gravel be for a path?
A garden path needs 50 mm of gravel if laid on a firm sub-base, or 75 mm if laid directly on soil. If you're using a weed membrane under the gravel, 50 mm is enough. Deeper than 100 mm and walking becomes difficult because the gravel shifts under your feet.
How many bulk bags of gravel do I need?
A standard bulk bag (also called a tonne bag or jumbo bag) holds 850 kg of gravel - about 0.57 m³. For a 30 m² driveway at 75 mm depth, that is 2.25 m³ = 3.4 tonnes = 4 bags without waste, or 5 bags with 10% wastage. The calculator outputs the exact number for your dimensions.
What is the cheapest type of gravel for a driveway?
Crushed stone 20 mm and crusher run (MOT Type 1) are usually the cheapest options per tonne. They are also the most hard-wearing. Pea gravel is more decorative but can be more expensive and tends to shift underfoot. For the sub-base layer, MOT Type 1 is the standard choice.
Do I need a sub-base under gravel?
For any driveway that takes vehicles, yes - a minimum 100 mm compacted sub-base of MOT Type 1 or similar. For footpaths and decorative garden beds, a sub-base is optional but recommended - it stops the gravel sinking into the soil. If you skip the sub-base, use a weed membrane and add 25 mm extra gravel depth.
How much does a tonne of gravel cover?
At 50 mm depth, 1 tonne of pea gravel covers about 13 m². At 75 mm depth, it covers about 8.8 m². At 100 mm depth, it covers about 6.6 m². The heavier the gravel type, the less area it covers per tonne because the same volume weighs more.
What is the best gravel for a garden path?
Pea gravel is the traditional choice - small, smooth, comfortable underfoot. Decomposed granite compacts hard and stays in place, making it ideal for paths on slopes. Limestone chips and slate chips are decorative and inexpensive. Avoid crushed stone with sharp edges on bare-foot paths.
How do I stop weeds growing through gravel?
Lay a woven weed membrane (not the cheap non-woven type) under the gravel. This stops weeds from below. Any weed that grows on top has come from seed blown in - spot-treat with a weedkiller or pull by hand. Do not use plastic sheeting - it prevents drainage and gravel will float on waterlogged soil.
Can I put gravel directly on soil?
You can, but the gravel will gradually sink into the soil and you'll need to top it up every year. The correct way is: compact the soil, lay a weed membrane, then add 50 - 75 mm of gravel on top. For heavy use, excavate 100 mm and add a compacted sub-base before the gravel.
What size gravel is best for a driveway?
For a driveway, use 14 - 20 mm gravel. Smaller gravel (below 10 mm) is uncomfortable underfoot and can get stuck in tyre treads. Larger gravel (above 40 mm) is difficult to walk on and tends to be less stable under vehicle loads. The 14 - 20 mm range is the standard for driveways.
How much does gravel weigh per square metre?
At 50 mm depth, pea gravel weighs about 75 kg per m². At 75 mm it is 112 kg/m². At 100 mm it is 150 kg/m². This matters for structural design if you're gravel-topping a balcony or roof deck - check the load-bearing limit first.
Is gravel cheaper than paving?
Yes - gravel is much cheaper to install than block paving, concrete or asphalt. A 30 m² gravel driveway typically costs 1/3 to 1/2 the price of block paving, and it needs less site prep. The trade-off is maintenance - gravel needs topping up every 2 - 3 years and weeding a few times a year.
What is MOT Type 1 and do I need it?
MOT Type 1 is a specific graded crushed stone sub-base material. It compacts to form a strong, stable layer that distributes vehicle loads and prevents the surface gravel from sinking into soft ground. For any vehicle-bearing driveway, use 100 - 150 mm of MOT Type 1 as a sub-base. For footpaths, 75 mm is enough.
References & Standards
- BS EN 13242 - Aggregates for unbound and hydraulically bound materials
- BS EN 13043 - Aggregates for bituminous mixtures and surface treatments
- BS 7533 - Pavements constructed with clay, natural stone or concrete pavers
- Highways Agency Manual of Contract Documents - Series 800 (Road pavements)
- ASTM D2940 - Standard Specification for Graded Aggregate Material for Bases
- ASTM D448 - Standard Classification for Sizes of Aggregate for Road and Bridge Construction
- AS 2758 - Aggregates and rock for engineering purposes (Australia)
- NIS 550 - Nigerian Industrial Standard Building Code