Gravel Calculator

Work out how much gravel you need for a driveway, path or garden bed: enter the length and width of the area and how deep you want the gravel, and the calculator shows the volume, the weight and how many bags to buy. It works in metric (metres and centimetres) or imperial (feet and inches), and it runs entirely in your browser: free, instant, no sign-in.

How the gravel calculator works

The maths is three multiplications. First the area: length × width. Then the volume: area × depth — a 10 m × 5 m area at 0.1 m deep is 5 m³. Then the weight: volume × density — at a typical loose-gravel density of 1,600 kg/m³, those 5 m³ weigh 8,000 kg, or 8 tonnes. Finally the bags: weight ÷ bag size, rounded up — 8,000 kg ÷ 25 kg bags = 320 bags exactly. In imperial units the same steps apply: a 20 ft × 10 ft area at 4 inches deep is 66.67 ft³ (2.47 yd³), which at 100 lb/ft³ weighs 6,667 lb (3.33 US tons), or 134 bags of 50 lb — rounded up from 133.3, because you cannot buy part of a bag.

The density figure is an assumption, not a fact about your gravel: real gravel density varies with the stone type, the size of the stones and how wet they are. The calculator uses 1,600 kg/m³ (100 lb/ft³) as a typical loose-gravel figure, and you can change it to whatever your supplier quotes. If in doubt, add about 5–10% extra to cover uneven ground and settling.

Ordering gravel without a number to work from usually ends one of two ways: a half-finished driveway and a second delivery, or a pile of leftover stone sitting in the garden for a year. The Gravel Calculator gives you that number before you order: enter the length and width of the area and how deep you want the gravel, and it shows the volume, the weight and how many bags to buy. It works in metric (metres and centimetres) or imperial (feet and inches), and the density is editable, so you can use your supplier’s figure instead of the typical one. It runs entirely in your browser — free, instant, no sign-in — and nothing you enter is uploaded anywhere.

The density the calculator starts with is a typical loose-gravel figure: about 1,600 kg/m³ (100 lb/ft³). Real gravel density varies with the stone type, the size of the stones and how wet they are, so treat the weight as a good estimate rather than an exact figure — and if your supplier quotes a density, type it in. As a safety margin, add about 5–10% extra to cover uneven ground and settling.

How to use the calculator, step by step

Three measurements and one choice are all it takes. The result updates live as you type.

• Step 1 — Pick your units. Tap “Metric” for metres and centimetres, or “Imperial” for feet and inches. The calculator remembers nothing between visits, so pick the units your tape measure uses.
• Step 2 — Enter the length and width. Measure the area you want to cover. A driveway 10 m long and 5 m wide is 50 m²; a path 20 ft long and 10 ft wide is 200 ft². For an irregular shape, measure the longest length and the widest width, or split the area into rectangles and add them up — see the tips below.
• Step 3 — Enter the depth. In metric, enter the depth in metres: 10 cm is 0.1 m, 5 cm is 0.05 m. In imperial, enter the depth in inches: a driveway usually needs about 4 inches, a garden path about 2 inches. Deeper gravel lasts longer but costs more, so this is the number that most changes your order.
• Step 4 — Check the density and bag size. The calculator starts with a typical loose-gravel density (1,600 kg/m³ or 100 lb/ft³) and a common bag size (25 kg or 50 lb). Change either one if your supplier quotes a different density or sells a different bag size — the results update straight away.
• Step 5 — Read the result. The big numbers are the volume and the bags: volume in cubic metres and litres (or cubic feet and cubic yards), weight in kilograms and tonnes (or pounds and US tons), and the number of bags — always rounded up, because you cannot buy part of a bag. The maths line under the result shows the working, so you can check it.

How the maths works

Three multiplications turn your measurements into an order:

• Area = length × width. A 10 m × 5 m driveway is 50 m². A 20 ft × 10 ft path is 200 ft².
• Volume = area × depth. The 50 m² driveway at 0.1 m deep needs 50 × 0.1 = 5 m³ — which is 5 × 1,000 = 5,000 litres. The 200 ft² path at 4 inches deep (4 ÷ 12 = 0.333 ft) needs 200 × 0.333 = 66.67 ft³, and 66.67 ÷ 27 = 2.47 yd³.
• Weight = volume × density. At a typical loose-gravel density of 1,600 kg/m³, 5 m³ weighs 5 × 1,600 = 8,000 kg, or 8 tonnes. At 100 lb/ft³, 66.67 ft³ weighs 66.67 × 100 = 6,667 lb, or 3.33 US tons.
• Bags = weight ÷ bag size, rounded UP. 8,000 kg ÷ 25 kg bags = 320 bags exactly. 6,667 lb ÷ 50 lb bags = 133.3, which rounds up to 134 bags — a partial bag cannot be bought, so the calculator always rounds the bag count up to the next whole bag.

The conversions the calculator uses are: 1 m³ = 1,000 litres; 1 tonne = 1,000 kg; 1 yd³ = 27 ft³; 1 US ton = 2,000 lb; 1 ft = 12 in.

Worked examples

Example 1 — metric driveway: 10 m × 5 m, 0.1 m deep. Area = 10 × 5 = 50 m². Volume = 50 × 0.1 = 5 m³ = 5,000 litres. Weight at 1,600 kg/m³ = 5 × 1,600 = 8,000 kg = 8 tonnes. Bags at 25 kg = 8,000 ÷ 25 = 320 bags.

Example 2 — imperial path: 20 ft × 10 ft, 4 in deep. Area = 20 × 10 = 200 ft². Depth in feet = 4 ÷ 12 = 0.333 ft. Volume = 200 × 0.333 = 66.67 ft³ = 66.67 ÷ 27 = 2.47 yd³. Weight at 100 lb/ft³ = 66.67 × 100 = 6,667 lb = 6,667 ÷ 2,000 = 3.33 US tons. Bags at 50 lb = 6,667 ÷ 50 = 133.3, rounded up to 134 bags.

Example 3 — small garden path: 6 m × 1 m, 5 cm deep. Area = 6 × 1 = 6 m². Depth = 5 cm = 0.05 m. Volume = 6 × 0.05 = 0.3 m³ = 300 litres. Weight at 1,600 kg/m³ = 0.3 × 1,600 = 480 kg. Bags at 25 kg = 480 ÷ 25 = 19.2, rounded up to 20 bags.

Example 4 — a different density: the same driveway at 1,400 kg/m³. The volume is unchanged — 5 m³ — but the weight is 5 × 1,400 = 7,000 kg = 7 tonnes, and the bags are 7,000 ÷ 25 = 280. A lighter stone needs fewer bags for the same volume, which is why the density matters and why the calculator lets you change it.

Example 5 — adding a 10% margin: the metric driveway again. The base volume is 5 m³. Adding 10% gives 5 × 1.1 = 5.5 m³. Weight at 1,600 kg/m³ = 5.5 × 1,600 = 8,800 kg = 8.8 tonnes. Bags = 8,800 ÷ 25 = 352. A 10% margin on a driveway costs little and saves a second delivery.

Common mistakes

• Mixing up centimetres and metres. 10 cm is 0.1 m, not 10 m — entering 10 for the depth would calculate a hundred times too much gravel. In imperial, enter the depth in inches, not feet: 4 inches, not 0.33 feet, unless you are sure of the conversion.
• Forgetting the depth entirely. Area alone tells you nothing: a 50 m² driveway needs 2.5 m³ at 5 cm deep and 5 m³ at 10 cm deep. Measure the depth you actually want, and remember the gravel will settle a little after it is laid.
• Using the wrong density. Gravel density varies by stone type, stone size and moisture — wet gravel is heavier than dry gravel of the same volume. The calculator’s 1,600 kg/m³ (100 lb/ft³) is a typical loose-gravel figure, not a guarantee. If your supplier quotes a density, use that figure instead.
• Rounding the bags down. 133.3 bags means 134 bags, not 133 — a partial bag cannot be bought, and 133 bags would leave you short. The calculator always rounds the bag count up.
• Ordering exactly the calculated amount. The ground is rarely perfectly flat, and gravel settles after it is laid and walked on. Add about 5–10% extra, especially on a driveway or any area that has not been levelled.
• Measuring a slope as if it were flat. On a slope, measure the length along the ground, not the horizontal distance — a sloped path is longer than its footprint, and the extra length needs extra gravel.

Related tools

The gravel calculator is a measurement tool, and three companion calculators cover the numbers around a project like this.

• Percentage Calculator — work out a percentage increase or decrease, for example adding the 5–10% safety margin to your gravel volume.
• Monthly Budget Calculator — plan a monthly budget and see what a home or garden project leaves you with.
• Currency Converter — convert a supplier’s quote into your own currency at the live rate, across 150+ currencies.

For all of ToolZana’s free tools, start at the ToolZana home page.

Tips for ordering gravel

• Measure twice, in two directions. Measure the length and the width at more than one spot — driveways and paths are rarely perfect rectangles, and the widest point is the one that decides how much you need.
• Split irregular areas into rectangles. An L-shaped area is two rectangles: calculate each one separately and add the volumes together. The same trick works for a path that bends — split it at the bend.
• Ask your supplier for their density. A supplier who sells by the tonne knows the density of the stone they sell. Their figure beats the calculator’s typical 1,600 kg/m³ every time, and it is the number they will use to work out your delivery.
• Order a little extra on a first job. About 5–10% covers uneven ground, settling and the odd barrow spilt on the way. A second delivery of a small amount usually costs more per tonne than adding it to the first order.
• Check the delivery access. A bulk delivery needs a lorry to get close to where the gravel is going; bags can be carried further. Knowing whether you are ordering loose or bagged gravel decides whether the bag count matters at all.
• Compact the base before you lay gravel. A firm, level base stops the gravel sinking into soft ground, which is the most common reason a job that looked right on paper ends up needing more stone.

The short version

The Gravel Calculator works out how much gravel you need from the length and width of the area and the depth you want: area = length × width, volume = area × depth, weight = volume × density, and bags = weight ÷ bag size, rounded up. A 10 m × 5 m driveway at 0.1 m deep needs 5 m³ (5,000 litres), which at a typical density of 1,600 kg/m³ weighs 8,000 kg (8 tonnes) — 320 bags of 25 kg. A 20 ft × 10 ft path at 4 inches deep needs 66.67 ft³ (2.47 yd³), which at 100 lb/ft³ weighs 6,667 lb (3.33 US tons) — 134 bags of 50 lb, rounded up from 133.3. The density is an assumption: real gravel varies by stone type and moisture, so use your supplier’s figure when you have one, and add about 5–10% extra for uneven ground and settling. The tool is free, runs entirely in your browser, and needs no sign-in.

Frequently Asked Questions

What is a gravel calculator?

A gravel calculator works out how much gravel you need for a driveway, path, patio or garden bed. You enter the length and width of the area and how deep you want the gravel, and it calculates the volume, the weight and how many bags to buy. This calculator works in metric (metres and centimetres) or imperial (feet and inches), and it lets you change the gravel density and bag size to match what your supplier sells.

How do I use the gravel calculator?

Pick metric or imperial at the top, then enter the length and width of the area and the depth of gravel you want. In metric, enter the depth in metres — 10 cm is 0.1 m. In imperial, enter the depth in inches — a driveway usually needs about 4 inches. The result appears as you type: volume in cubic metres and litres (or cubic feet and cubic yards), weight in kilograms and tonnes (or pounds and US tons), and the number of bags, rounded up. Check the density and bag size fields too — they start with typical values, and you can change them to match your supplier.

How much gravel do I need for a driveway?

It depends on the size of the driveway and the depth. A 10 m × 5 m driveway at 0.1 m (10 cm) deep needs 5 m³ of gravel, which weighs about 8,000 kg (8 tonnes) at a typical density of 1,600 kg/m³ — 320 bags of 25 kg. A smaller driveway, 6 m × 3 m at the same depth, needs 1.8 m³, about 2,880 kg, or 116 bags of 25 kg (2,880 ÷ 25 = 115.2, rounded up). Enter your own measurements in the calculator for an exact figure, and add about 5–10% extra for uneven ground.

How deep should gravel be?

For a driveway, about 10 cm (4 inches) is the usual depth — deep enough to spread evenly and stay put under car tyres, but not so deep that it is hard to walk or drive on. For a garden path, about 5 cm (2 inches) is usually enough, and for a decorative border or garden bed, 3–5 cm (1–2 inches) will cover the ground. Deeper gravel lasts longer and hides the ground better, but every extra centimetre adds volume and weight, so it costs more. The calculator shows you exactly how much each extra centimetre adds.

How many bags of gravel do I need?

Divide the total weight by the bag size and round up. A 10 m × 5 m driveway at 0.1 m deep weighs 8,000 kg at a typical density of 1,600 kg/m³, so at 25 kg per bag you need 8,000 ÷ 25 = 320 bags. A 20 ft × 10 ft path at 4 inches deep weighs 6,667 lb, so at 50 lb per bag you need 6,667 ÷ 50 = 133.3, rounded up to 134 bags. The calculator does this division and the rounding up for you — a partial bag cannot be bought, so the answer is always a whole number of bags.

How much does gravel weigh?

At a typical loose-gravel density of about 1,600 kg/m³, one cubic metre of gravel weighs about 1,600 kg (1.6 tonnes), and one cubic yard weighs about 2,700 lb (1.35 US tons) at the equivalent density of 100 lb/ft³. Real gravel varies: the exact figure depends on the stone type, the size of the stones and how wet they are, so a supplier’s own density is always more accurate than the typical figure. If your supplier quotes a different density, enter it in the calculator and the weight will update.

How do I convert cubic metres to cubic yards?

One cubic metre is about 1.308 cubic yards, and one cubic yard is about 0.765 cubic metres. To convert, multiply cubic metres by 1.308 to get cubic yards, or multiply cubic yards by 0.765 to get cubic metres. For example, 5 m³ is 5 × 1.308 = 6.54 yd³, and 2.47 yd³ is 2.47 × 0.765 = 1.89 m³. The calculator shows both units for you: the metric result gives cubic metres and litres, and the imperial result gives cubic feet and cubic yards (1 yd³ = 27 ft³).

What density should I use for gravel?

Use a typical loose-gravel density of about 1,600 kg/m³ (100 lb/ft³) unless your supplier gives you a different figure — that is the default the calculator starts with. Density varies with the stone type, the size of the stones and the moisture: wet gravel is heavier than dry gravel of the same volume, and dense stone like granite is heavier than light stone. The volume does not change with density, only the weight and the bag count do, so if you are ordering loose gravel by volume, the density matters less than if you are ordering by weight or in bags.

How much extra gravel should I order?

Add about 5–10% extra on top of the calculated amount. The ground is rarely perfectly flat, gravel settles after it is laid and walked on, and a little is always lost in transport and spreading. On a 5 m³ job, 10% extra is 0.5 m³, taking the order to 5.5 m³ — 8,800 kg, or 352 bags of 25 kg instead of 320. A second delivery of a small amount usually costs more per tonne than adding it to the first order, so a modest margin is cheaper than running short.

Can I use the gravel calculator for a path or a garden bed?

Yes — the calculator works for any area, because it only needs a length, a width and a depth. A garden path 6 m long and 1 m wide at 5 cm deep needs 0.3 m³ (300 litres), about 480 kg, or 20 bags of 25 kg. A garden bed 3 m by 2 m at 5 cm deep needs 0.3 m³ as well. For a round bed, measure the diameter, use half of it as the radius, and treat the area as 3.14 × radius × radius — or just use the longest length and widest width, which gives a slightly generous figure.

How do I measure an irregular area?

Split it into rectangles and add them up. An L-shaped driveway is two rectangles: measure each one, work out its volume, and add the two volumes together. A path that bends can be split at the bend the same way. For a curved edge, measure the longest length and the widest width and use those — the answer will be slightly generous, which is safer than coming up short. On a slope, measure the length along the ground rather than the horizontal distance, because the sloped surface is longer than its footprint.

Is the gravel calculator free?

Yes — the Gravel Calculator is completely free, with no sign-in and no limits. It runs entirely in your browser, so nothing you enter is uploaded anywhere, and you can use it as often as you like, for driveways, paths, patios and garden beds of any size.