How many bulk bags of gravel do I need?
Published · Updated · By Sai Nath
Work out the tonnes you need, add about 10 percent, then divide by one bag's weight and round up. A 10 m × 3 m area at 75 mm is 3.375 t, or 3.713 t with the allowance. With an example 800 kg bag that is 4.64, so 5 bags. Use the weight on your supplier's listing.
How do I work out how many bags I need?
- Find the volume. Length × width × depth, all in metres. Use the depth after compaction, not the loose depth.
- Convert to tonnes. Volume × density (kg/m³) ÷ 1,000. One tonne is 1,000 kg (NIST SP 811, Appendix B.8; checked on 28 October 2026).
- Add an allowance. About 10 percent covers spillage, uneven ground and settling. It is a rule of thumb, not a standard.
- Divide by the bag weight. Use the figure on the listing for the exact product you are buying, in tonnes (800 kg is 0.8 t).
- Round up. You cannot buy 4.64 bags. Order 5.
If your site is bigger than a path or a bed, the first three steps are set out in full in how much gravel do I need.
How many kg or m³ is in a bulk bag of gravel?
It depends on the bag, and there is no single answer. Suppliers sell bulk bags by volume or by weight. Jewson's bulk bag gravel search, for example, offers size filters of "Bulk Bag - 500L" and "Bulk Bag - 800kg" side by side (Jewson search; checked on 28 October 2026). Two of its product pages, for 20 mm gravel/shingle and golden gravel, state no weight, volume or coverage, and add that bag weight may vary slightly (checked on 28 October 2026). So read the weight, or the litres, off the listing for the product you are buying. If you can't find it, ask the supplier before you order.
To convert between the two units you need the density:
- Litres to kg: litres ÷ 1,000 × density. A 500 L bag at 1,500 kg/m³ is 0.5 × 1,500 = 750 kg.
- kg to m³: kg ÷ density. An 800 kg bag at 1,500 kg/m³ is 0.533 m³. A 1,000 kg bag is 0.667 m³.
The 1,500 kg/m³ is the figure MeisterCalc's Gravel calculator starts at. It is used here to show the arithmetic, not as a measured density for any product. Use your supplier's figure.
A worked example: 10 m × 3 m at 75 mm
Volume: 10 × 3 × 0.075 = 2.25 m³. Weight at 1,500 kg/m³: 2.25 × 1,500 ÷ 1,000 = 3.375 t. With 10 percent on top: 3.375 × 1.10 = 3.7125, which MeisterCalc shows as 3.713 t. Now divide by the bag. The 800 kg bag below is an example only. Swap in your own listing's weight.
3.713 ÷ 0.8 = 4.64, so order 5 bags.
How much does a bulk bag of gravel cover?
Coverage per bag is bag weight ÷ (density × depth in metres), in square metres. It changes with depth, so any one figure quoted without a depth is of little use. At 1,500 kg/m³:
| Compacted depth | 500 L bag (750 kg) | 800 kg bag | 1,000 kg bag |
|---|---|---|---|
| 25 mm | 20.0 m² | 21.3 m² | 26.7 m² |
| 50 mm | 10.0 m² | 10.7 m² | 13.3 m² |
| 75 mm | 6.7 m² | 7.1 m² | 8.9 m² |
| 100 mm | 5.0 m² | 5.3 m² | 6.7 m² |
Worked sum for the 800 kg bag at 75 mm: 0.8 ÷ (1,500 ÷ 1,000 × 0.075) = 0.8 ÷ 0.1125 = 7.1 m². These are the arithmetic for example bag sizes at an assumed density. They include no allowance, so divide your area by the figure, then add your 10 percent. If your stone's density is 1,400, multiply each figure by 1,500 ÷ 1,400: the 800 kg bag at 75 mm then covers 7.1 × 1,500 ÷ 1,400 = 7.6 m². If it is 1,800, multiply by 1,500 ÷ 1,800: 7.1 × 1,500 ÷ 1,800 = 5.9 m². Both densities are made up to show the effect. For tonnes per square metre, see how many square metres a tonne of gravel covers.
Do I need to add extra, and when does it change the count?
Yes, and sometimes it changes the answer. Say the job needs exactly 4.0 t and the bag is 0.8 t. That is 5 bags with no allowance. With 10 percent, 4.4 ÷ 0.8 = 5.5, so 6 bags. A short load costs a second delivery. A spare half bag costs less than that, and you can use it to top up low spots.
Does the stone type change the number?
Yes, through the density. A bag is filled to a weight or a volume, while the job is measured in volume. A denser stone weighs more per cubic metre, so a bag of it covers less. Moisture and compaction change the figure again. So this page gives no density table for gravel. Ask your supplier for the tonnes per cubic metre of the exact product, and whether the figure is loose or compacted. The conversion both ways is in cubic metres to tonnes.
What mistakes make people over- or under-order?
- Assuming a standard bag. Weights and sizes differ between products and suppliers, and bags may vary slightly from the stated weight.
- Using loose depth. Gravel loses volume when it is compacted. Work from the finished, compacted depth.
- Using the wrong density. The default 1,500 kg/m³ is a placeholder. Use the supplier's figure.
- Rounding down. 4.2 bags is 5 bags.
- Mixing up litres and kg. A 500 L bag and an 800 kg bag are not the same thing.
Paving or bedding under it? The same method works for the layer beneath: see how much sand for paving.
How much does a bulk bag of gravel cost?
It varies by supplier, product and delivery, so this page quotes no price. Compare the price per tonne, not per bag, because bags differ in weight.
Doing it in MeisterCalc
- Open MeisterCalc and tap Gravel on the home screen (Home ▸ Gravel).
- Enter Length, Width and Depth. Millimetres are the default; feet and inches are under Settings ▸ Units ▸ Default units.
- Change Density (kg/m³) from 1,500 to your supplier's figure.
- Read Volume (m³), Weight (t) and Order (+10%) (t).
- Divide the Order (+10%) figure by your bag weight in tonnes, and round up.
For the 10 m × 3 m × 75 mm example the card reads Volume 2.250 m³, Weight 3.375 t and Order (+10%) 3.713 t.
What the calculator doesn't do
- It does not count bags. It gives tonnes, and you divide by the bag weight.
- The Order (+10%) row is always 10 percent. The optional Wastage slider (0 to 30 percent) only changes the cost figure, which needs a Price per tonne.
- No compaction or moisture setting. Put the right density in instead. Density must be between 100 and 5,000 kg/m³.
- It does not know your supplier's densities or bag sizes, and it does not tell you what your site needs.
Try it
Concrete, Stairs and Check Square are the free calculators. Gravel is among the other twelve, which unlock with a weekly subscription that starts with a 3-day free trial, or with a one-time lifetime unlock; Google Play shows the prices in your currency. Calculations work offline, on Android 7.0 or later. There's no iPhone version yet; you can join the iOS waitlist.
Sources
- NIST Guide to the SI, Appendix B.8: tonne = 1,000 kg. Checked on 28 October 2026.
- Jewson, bulk bag gravel search: size filters in litres and kg. Checked on 28 October 2026.
- Jewson, 20 mm gravel/shingle bulk bag and golden gravel bulk bag: no stated weight, volume or coverage; bag weight may vary slightly. Checked on 28 October 2026.