Fill Dirt Calculator
| Project | Fill to | Order | Weight | Settles to |
|---|---|---|---|---|
| Lawn low spot 12 x 30 | 4 in | 5.1 yd³ | 6.6 t | 3.5 in |
| Pool void 16 x 32 | 3 ft avg | 65.4 yd³ | 85.0 t | 31.3 in |
| Raised pad 30 x 40 | 12 in | 55.6 yd³ | 72.2 t | 9.6 in |
| Grade strip 60 x 4 | 8 in | 6.8 yd³ | 8.8 t | 7.0 in |
Fill dirt is the subsoil of the ordering world: it is the mineral stuff beneath the topsoil - sand, silt, clay, small rock - and its whole job is volume that stays put, which is why good fill dirt is judged by what it does NOT have: no organics to rot and settle, no construction debris, no gypsum clumps. It goes under things - lawns, pool voids, foundation grades, building pads - and the four to six inches of settled topsoil goes on top of it, never the reverse.
The math is the family yards-times-depth with one twist fill jobs never escape: compaction. Loose delivered dirt packs down, so you order more than the void holds - 15 percent is a working allowance for a tamped lawn fill, and engineered fills compacted in 6-to-8-inch lifts against a spec can demand 25 percent or more, set by the proctor test the geotechnical report runs. The flip side is settling: fill that is just dumped and left alone keeps sinking for a season or two, typically 10 to 20 percent of its loose depth, which is why a low spot filled flush in May is a shallow bowl by fall.
Money context is federal: the USGS Mineral Commodity Summaries prices construction sand and gravel - the family fill dirt is bought and sold in - at an average $14.50 per metric ton in the 2025 estimate, with metro shortages pushing urban quotes above that line. What varies the delivered price most is screening and haul: screened clean fill costs more per yard than pit-run, and anything advertised as free fill dirt deserves the same question as paid dirt - what is in the truck, and is it tested.
How to use
- Measure the void in feet and the depth in inches - fill to final grade, not to the loose height you hope it becomes.
- Pick the compaction allowance honestly: 15 percent for a tamped lawn fill, 25 percent for an engineered lift-compacted pad.
- Check the settled depth before ordering - a 12-inch fill at 25 percent compaction settles to about 9.6 inches, so grade stakes are set to the finished line, not the loose pile.
Frequently asked questions
How much fill dirt do I need for a low spot?
Square feet times depth in inches, divided by 324, gives cubic yards; add 15 percent for compaction and you have the order. A 12-by-30-foot low spot filled 4 inches works out to about 4.4 yards raw, call it 5.1 yards delivered - roughly 7 tons on a single dump truck.
How much does fill dirt settle?
Fill that is dumped and left uncompacted typically settles 10 to 20 percent of its loose depth over the first season as air voids collapse and organics rot out. Fill compacted in 6-to-8-inch lifts with a plate compactor settles little enough that engineers design to it - that is the difference between a lawn fill and a pad a structure sits on.
Is fill dirt the same as topsoil?
No, and the order matters. Fill dirt is the sterile mineral subsoil that carries load; topsoil is the biologically active layer plants root in. Backfill a yard entirely with topsoil and it settles and weeds as it rots; cap fill dirt with topsoil and the lawn has both a stable base and a living top four to six inches deep.
How many tons is a yard of fill dirt?
About 1.2 to 1.4 tons per cubic yard delivered loose depending on moisture - the same rain rule as sand, a wet pile weighs more at the same volume. A full-size single-axle dump load of 10 to 12 yards is roughly 14 to 16 tons, which is why per-ton quotes and per-yard quotes must be converted before you compare them.
Can I use fill sand instead of fill dirt?
Sometimes - sand drains where clay dirt holds water, which makes fill sand the choice around foundations and under hardscape. But sand fills wash and migrate without containment, so for a lawn fill that plants will root into, a mixed mineral dirt holds moisture and shape better. The sand calculator prices the sandy side of the same pit.
What should I ask a fill dirt supplier?
Three things: what is in it - clean mineral dirt, screened or pit-run; what it is free of - organics, construction debris, gypsum; and whether the load is tested if it goes anywhere near a structure. Urban shortages are real - USGS expects metro prices to keep climbing - and the cheapest load in town is rarely the one that settles least.