Fill Dirt Compaction Calculator

Fill dirt compaction calculator: compacted ÷ (1 − loss)

This fill dirt compaction calculator works backward from the packed volume you need to the loose volume you should order. The formula is loose yards to order = compacted yards ÷ (1 − loss % ÷ 100). With the defaults, 20 compacted yards at a 20% loss gives 20 ÷ 0.80 = 25.00 loose yards.

What “compaction loss” means here

Think of a loose truckload as 100 buckets. After rolling, those 100 buckets only fill 80 buckets of space. The 20 buckets that “disappeared” were air. That is a 20% compaction loss.

The calculator divides, rather than multiplies, for a reason. Adding 20% to 20 yards gives 24, but 24 loose yards at 20% loss only compacts to 19.2. Dividing by 0.80 gives the exact 25 yards that compact to 20.

Worked examples

1. Default: 20 yd³ compacted, 20% loss

• Remaining fraction: 1 − 0.20 = 0.80
• Loose to order: 20 ÷ 0.80 = 25.00 yd³

2. Building up a patio pad: 30 × 20 ft, 1 ft deep, 25% loss

• Compacted volume: 30 × 20 × 1 = 600 cu ft ÷ 27 = 22.22 yd³
• Remaining fraction: 1 − 0.25 = 0.75
• Loose to order: 22.22 ÷ 0.75 = 29.63 yd³

3. Small low spot: 12 yd³ compacted, 15% loss

• Loose to order: 12 ÷ 0.85 = 14.12 yd³

Loose fill reference table

Loose yards needed for each compacted volume:

Compacted volume	10% loss	15% loss	20% loss	25% loss
5 yd³	5.56	5.88	6.25	6.67
10 yd³	11.11	11.76	12.50	13.33
20 yd³	22.22	23.53	25.00	26.67
50 yd³	55.56	58.82	62.50	66.67

Each step up in loss raises the order faster as the loss grows, because you are dividing by a smaller number. Going from 20% to 25% loss on 50 compacted yards adds more than 4 loose yards, close to half a truckload.

How to find the compacted volume

1. Measure the area to fill: length × width in feet.
2. Measure the depth to raise in feet. Use the average of several readings for an uneven hollow.
3. Multiply for cubic feet, then divide by 27 for cubic yards.
4. Enter that figure as the compacted volume. The cubic yard calculator can do steps 1 to 3.

Turning loose yards into deliveries

Ask your supplier what a full truck holds. If a truck carries 10 loose yards, the default order of 25 yards is two full loads plus a partial. It is often cheaper to take three full loads and spread the extra than to pay for a small third delivery.

Have the trucks dump as close to the fill area as the ground allows. Spread and compact each lift before the next load arrives, so you can see whether the loss figure is holding up. If you reach grade with material left over, the loss was lower than you assumed; if you run short, it was higher. Either way, note it for next time.

Common fill compaction mistakes

• Ordering the hole size. This is the most common error and almost always leaves you short.
• Adding the percentage instead of dividing. As shown above, adding 20% under-orders.
• Dumping it all at once. Thick layers compact on top and stay loose below. Place and compact in lifts.
• Compacting very dry or very wet soil. Both resist compaction. Soil near its ideal moisture packs tightest.
• Using topsoil as structural fill. Organic soil keeps settling as it breaks down. Use clean fill under slabs, patios, and foundations.
• Burying debris. Stumps, roots, and construction scrap rot or shift under fill and leave sinkholes later. Clear them out before placing the first lift.
• Skipping the plate compactor. Letting fill “settle on its own” can take seasons and leaves dips.

Related calculators

The fill dirt calculator turns an area and depth into yards and tons. For grading jobs that reuse site soil, check the balance with the cut and fill calculator. For trenches around pipe, try the backfill calculator.

A planning estimate using a typical loss range. Real compaction depends on soil type, moisture, and equipment; structural fill should follow an engineer’s specification.