EXCAVATION & PAVING · FIELD TOOL

Backfill Quantity Calculator

Compacted backfill = excavation − structures. To fill 90 m³ compacted you need 90 ÷ (1 − 10% shrinkage) = 100 m³ of soil as it lies in the ground, which is 125 m³ loose in trucks (25% swell) and weighs about 180 t.

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Compacted backfill

90.0m³

Bank volume needed	100.0 m³
Loose volume to haul	125.0 m³
Weight of fill	180.0 t
Truck loads	13 loads

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Working

Compacted backfill = 120.0 − 30.0 = 90.0 m³
Bank volume = compacted ÷ (1 − 10%) = 100.0 m³
Loose volume = bank × (1 + 25%) = 125.0 m³
Weight = bank × density = 180.0 t; loads = ⌈125.0 ÷ 10.0⌉ = 13

Results are estimates for planning and material ordering only. They are not a substitute for structural design or approval by a qualified engineer. Read the full disclaimer.

Formulas

Compacted   = excavation − structures
Bank        = compacted ÷ (1 − shrinkage %)
Loose       = bank × (1 + swell %)
Weight      = bank × bank density

Worked Example

Excavation 120 m³, structures 30 m³, common earth (25% swell, 10% shrinkage, 1,800 kg/m³):

Compacted = 120 − 30 = 90 m³
Bank = 90 ÷ 0.90 = 100 m³
Loose = 100 × 1.25 = 125 m³ → 13 loads at 10 m³
Weight = 100 × 1,800 = 180 t

Typical Swell and Shrinkage

Material	Swell (bank → loose)	Shrinkage (bank → compacted)
Sand / gravel	10–15%	5–10%
Common earth	20–30%	10–15%
Clay	30–40%	10–20%
Rock fill	50–65%	bulks 20–30% instead

Use test results from your site where you have them.

Bags of Soil per Cubic Yard

Bag size	Bags per cubic yard
0.75 ft³	36
1 ft³	27
1.5 ft³	18
2 ft³	14
40 L	20
50 L	16

Frequently Asked Questions

How do I calculate backfill quantity?

Take the excavation volume and subtract everything built inside it below ground: footings, walls, pipes, tanks, blinding. The rest is the compacted backfill volume.

What is the difference between bank, loose and compacted volume?

Bank is soil as it lies in the ground. Loose is the same soil after digging (bigger, because it swells). Compacted is the volume after rolling (usually smaller than bank, because it shrinks).

How much extra fill should I order?

Divide the compacted volume by (1 − shrinkage) to get bank volume, then multiply by (1 + swell) for the loose volume you buy or haul. For common earth that is about 1.4 × the compacted volume.

How many bags of soil are in a cubic yard?

A cubic yard is 27 ft³ (765 L), so 27 bags of 1 ft³, 18 bags of 1.5 ft³, about 14 bags of 2 ft³, 36 bags of 0.75 ft³ or 20 bags of 40 L.

How do I calculate cubic yards of dirt?

Multiply length × width × depth in feet and divide by 27. An area 20 × 10 ft filled 6 in (0.5 ft) deep is 100 ft³ ÷ 27 = 3.7 yd³. Order extra for settling if the soil will be compacted.

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