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How much area will your bags of gravel cover?

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Convert between tonnes, bulk bags, and small bags

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MOT Type 1 quantity with compaction allowance

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Calculator pre-set for 50mm driveway depth

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Calculator pre-set for 30mm path depth

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Calculator pre-set for 40mm patio depth

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Calculator pre-set for decorative borders

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Full 2026 cost breakdown — DIY vs professional

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Step-by-step from excavation to finished surface

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Gravel vs Bark Mulch

Cost, lifespan, and which suits your borders

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Bag to Area Converter

Already bought bags of gravel? Find out how much ground they will cover. Or work backwards from your area to see how many bags you need.

cm

Area Covered

3.33m²

Volume

0.133m³

Total Weight

200kg

10 x 20kg bags = 200kg of Slate Gravel (20mm), covering 3.33m² at 4cm depth.

Quick Reference: 20kg Bags per m²

Based on standard gravel density of 1,500 kg/m³. Heavier aggregates like MOT Type 1 require more bags per m².

Depth20kg Bags per m²Bags for 5 m²Bags for 10 m²
30mm2.31223
40mm3.01530
50mm3.81938
60mm4.52345

Worked Examples

Topping Up a Garden Border

You have 15 bags of 20kg Plum Slate and want to know the area covered at 40mm depth.

  • Total weight: 15 × 20 = 300 kg
  • Volume: 300 ÷ 1,500 = 0.2 m³
  • Area at 40mm: 0.2 ÷ 0.04 = 5 m²

Covering a Small Patio

You need to cover 8m² of patio at 50mm depth with Golden Gravel (1,600 kg/m³).

  • Volume: 8 × 0.05 = 0.4 m³
  • Weight: 0.4 × 1,600 = 640 kg
  • Bags needed: 640 ÷ 20 = 32 bags

Understanding Bag Coverage

The area a bag covers depends on three factors: the weight of the bag, the density of the gravel type, and the depth you lay it at. Heavier aggregates like MOT Type 1 produce less volume per kilogram, so they cover a smaller area at the same depth compared to lighter decorative gravel. Always check your gravel type when estimating coverage.

Small Bags vs Bulk Bags

Individual 10–20kg bags are convenient for small areas and easy to carry, but they cost significantly more per kilogram. For anything larger than a few square metres, ordering in bulk (500kg or 1000kg) offers far better value. Suppliers like Stones4Gardens, deliver bulk bags on a pallet directly to your driveway.

Need a Full Calculation?

Our main calculator gives you tonnage, bag counts, cost estimates, and a visual breakdown based on your exact measurements.

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Frequently Asked Questions

How much area does a 20kg bag of gravel cover?
A 20kg bag of standard gravel (density 1,500 kg/m³) covers approximately 0.33m² at 40mm depth, or about 0.44m² at 30mm depth. Coverage varies by stone type and depth.
How many bags of gravel do I need for 10m²?
At 40mm depth with standard gravel, you need roughly 60 bags of 20kg or 48 bags of 25kg. For a driveway at 50mm depth, you would need about 75 bags of 20kg. Use the converter above for an exact figure.
Is it cheaper to buy bulk bags or small bags?
Larger quantities (500kg or 1000kg) are significantly cheaper per kilogram than 10–20kg bags. If you need a large amount, ordering in bulk is almost always better value.
How do I know what density to use?
Standard gravel and pebbles have a density around 1,500 kg/m³, while MOT Type 1 sub-base is denser at about 2,000 kg/m³. The converter lets you choose your material type for an accurate result.
How many 20kg bags do I need per square metre?
At 40mm depth with standard gravel (1,500 kg/m³), you need about 3 bags of 20kg per square metre. At 50mm depth, that rises to roughly 3.75 bags per m². Use the converter above for exact figures based on your gravel type.
Can I mix different bag sizes in one order?
Yes — many suppliers let you combine bag sizes. A common approach is to order the bulk of your material in 1,000kg bags and top up with 20kg bags for precise coverage. This gives you both value and flexibility.
How do I calculate bags for an irregular area?
Split your area into rectangles, calculate each separately, then add the totals. Our main calculator has a multi-area mode that does this automatically — just add each rectangle as a separate area.
What's the difference between 10kg and 20kg bags?
10kg bags are easier to carry and ideal for small, precise areas like borders and pot toppings. 20kg bags offer better value per kilogram and are the standard for most garden and path projects. For anything over a few square metres, 20kg bags or bulk orders are more economical.

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Gravel Depth Guide

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Tonnes to Bags Converter

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