Ballast Calculator

All-in ballast for mixing concrete: tonnes and m³ for your area and depth, and how many 25 kg or 850 kg bulk bags to order.

All-in ballast is sand and gravel (typically up to 20 mm) ready mixed together, so you only need to add cement and water to make concrete. It's the usual way to mix concrete by hand or in a mixer in the UK, and it's sold in 25 kg bags and 850 kg bulk bags. Enter the area and depth of the job and this calculator gives the tonnes and m³ of ballast and the bags to order. To work out ballast and cement together for a concrete mix, use the cement calculator, which includes 1:5 and 1:6 cement-to-ballast mixes.

Units

Bag sizes

Material

Area

Shape

Length

Width

Depth

Density (tonnes per m³)

t/m³

Extra for waste and compaction

Bag size

Volume: 1.26 m³
Weight: 2.08 tonnes
Bags: 84

Bags needed by size
25 kg bag	84
850 kg bulk bag	3

Price (optional)

Price is per

How it was worked out

Area: 4 m × 3 m = 12 m²; × 100 mm (0.1 m) deep = 1.2 m³
Plus 5% extra = 1.26 m³
1.26 m³ × 1.65 t/m³ = 2.08 tonnes (2,079 kg)
2,079 kg ÷ 25 kg per bag = 83.16, rounded up to 84 bags

Typical weights of common materials

Material	t/m³	tons/yd³	lb/ft³
Concrete	2.40	2.02	150
Gravel	1.60	1.35	100
Pea gravel	1.60	1.35	100
Crushed stone / crushed rock	1.60	1.35	100
River rock	1.50	1.26	94
Landscape rock / pebbles	1.50	1.26	94
Crushed limestone	1.60	1.35	100
Decomposed granite	1.50	1.26	94
Crusher run	1.60	1.35	100
Road base	1.70	1.43	106
Crusher dust	1.50	1.26	94
Aggregate (20 mm)	1.60	1.35	100
All-in ballast	1.65	1.39	103
MOT Type 1 sub-base	1.80	1.52	112
Sand	1.60	1.35	100
Topsoil	1.30	1.10	81
Garden soil	1.30	1.10	81
Fill dirt	1.40	1.18	87
Mulch	0.35	0.29	22
Bark chippings	0.30	0.25	19
Asphalt (compacted)	2.32	1.96	145

Loose, as-delivered figures; asphalt and concrete are as laid. Moisture, stone size and source change the real weight, so use your supplier's figure when you have it. Tons are US short tons (2,000 lb).

Common use cases

Ballast for a concrete shed base, path or fence post holes
Bulk bags for a foundation or a large pour mixed on site
Bedding and filling where a well-graded mix is needed
Working out how many bags fit in a car or van load

How to use

Choose feet and inches or metres and millimetres, and the country whose bag sizes you want.
Enter the length and width of the area, or switch the shape to a circle, triangle or a known area. Use Add another area for L-shapes and separate beds.
Enter the depth of ballast. For concrete, enter the slab or footing size here, or use the cement calculator for ballast and cement together.
Check the density and the extra allowance. Change the density if your supplier quotes a different figure.
Read the volume, weight and bag count, and add a price per ton, cubic yard, m³ or bag for a cost estimate.

FAQ

How much ballast do I need for a cubic metre of concrete?

With a 1:5 cement-to-ballast mix and a dry-volume factor of 1.54, about 1.28 m³ of ballast, roughly 2.1 tonnes or two and a half 850 kg bulk bags, plus about 15 × 25 kg bags of cement. The cement calculator shows the working.

What ratio of cement to ballast?

UK guides commonly give 1 part cement to 5 parts all-in ballast for general-purpose concrete, and a weaker 1:6 for foundations and mass concrete. Follow your plans for structural work.

How much does ballast weigh?

Around 1.65 tonnes per m³ loose, more when wet. A 25 kg bag is roughly 15 litres.

Common use cases

How to use

FAQ

How much ballast do I need for a cubic metre of concrete?

What ratio of cement to ballast?

How much does ballast weigh?

Related tools