How much soil do I need to remove for a retaining wall?

You dig a level base trench along the wall, roughly as wide as the block is deep plus a little room behind for drainage stone, and deep enough for the buried base course plus the compacted base pad below it. For a 40 ft wall with a 2 ft wide trench about 14 in deep that is around 3.5 cubic yards in the ground, which bulks up to about 4.3 cubic yards of loose soil once it is dug out. Enter your wall to get your own figure.

Why is there more soil to haul than I dug out?

Soil expands when you excavate it because digging breaks up the compacted, settled ground and adds air gaps. This is called swell, and for typical soils it is about 20 to 30 percent. So 3.5 cubic yards measured in the ground becomes roughly 4.3 cubic yards of loose material in the truck or pile. Swell adds volume but not weight, so haul volume goes up while the tonnage stays the same.

Can I put retaining wall soil in a dumpster?

You can, but soil is heavy and most dumpsters have a low weight limit, often around 2 tons on a small 10-yard can, with steep overage fees. A few cubic yards of dirt can weigh more than the dumpster is rated to carry, so you may need several cans or a smaller fill even though the volume looks like it fits. That is why contractors usually haul soil away in dump trucks rather than dumpsters, and this calculator sizes both by weight as well as volume.

How deep do you excavate for a retaining wall base?

Deep enough to bury the bottom course of block below finished grade and to sit it on a compacted base of crushed stone. A common rule buries about one inch of block for every foot of wall height, or one full course, on top of roughly 6 in of base stone. So a low wall often needs a base trench about 12 to 18 in deep. Tall or loaded walls are engineered and may need much deeper over-excavation.

Retaining Wall Excavation Calculator

How much soil you dig out of the base trench, how much it swells, what it weighs, and how many dump-truck loads or dumpsters it takes to haul away — with the haul-vs-dumpster cost decision most people get wrong because dirt is heavier than it looks.

Dig profile

Wall length (ft)

Exposed height (ft)

Base course buried (in)

Base stone below (in)

Trench width (ft)

How wide you open the base trench — block depth plus working room behind for drainage stone. Reinforced walls open wider.

Fine-tune swell, reuse, truck & dumpster sizes & prices

Soil behaviour

Swell when dug (%)

Reused on site (%)

Soil weight (tons/cu yd)

Dump-truck load (cu yd)

Dumpster — soil is heavy, so weight usually caps the fill before volume does

Dumpster volume (cu yd)

Dumpster weight limit (tons)

Unit prices — leave dig blank if you'll dig it yourself

Excavation / cu yd

Haul-off / load

Dumpster / each

You excavate a level base trench, set the buried base course on compacted stone, and haul the dug soil away — bulked up by swell. Cross-section is schematic, not to scale.

↗ Retaining Wall Excavation Calculator by GRLab — free retaining-wall planning tools

The dig is the line item people forget to price

Most retaining-wall estimates jump straight to blocks, caps and gravel and quietly assume the hole is already there. But before any of that goes in, you have to open a level base trench along the whole wall, and then get rid of the soil that came out of it. On a small DIY wall that's an afternoon with a shovel; on anything bigger it's machine time plus a real haul-off bill. This tool sizes that dig and the spoil so you can budget it, rent the right truck or dumpster, and not get surprised when a few "small" cubic yards of dirt turn out to weigh several tons.

How each number is worked out

Base-trench volume: length × trench width × trench depth, where trench depth is the buried base course plus the compacted base stone below it. That's the soil measured in the ground (its "bank" volume).
Swell: digging breaks up settled soil and adds air, so it bulks up — typically 20–30%. Loose (haul) volume = bank volume × (1 + swell). This is the volume that actually fills a truck or pile.
Spoil weight: weight comes from the bank volume × soil density (about 1.35 tons/cu yd for common soil). Swell adds volume but not weight, so the tonnage is the same whether it's packed or loose — which is exactly why heavy soil defeats dumpster volume ratings.
Truck loads & dumpsters: loose volume ÷ truck capacity gives dump-truck loads. Dumpsters are sized by both volume and weight limit, and we take whichever needs more cans — because a "10-yard" dumpster full of dirt usually hits its weight cap long before it's full.
Reused on site: if you're regrading and keeping some spoil, set the reuse % to cut the haul volume and weight (you still dig it all, so the excavation cost is unchanged).
Haul vs dumpster: both routes are priced — loads × haul rate versus dumpsters × rental — and the cheaper one is flagged and rolled into the total with the dig.

This tool sizes the base/leveling trench every wall needs, plus the spoil haul-off. It doesn't include the base stone tonnage itself (see the full takeoff) or, for reinforced walls, the large over-excavation of the geogrid zone behind the wall (see the geogrid tool for that footprint). Every field is editable; defaults follow common segmental-wall practice, not a specific design.

Tall or loaded walls need an engineer. Walls over 4 ft (1.2 m), or shorter walls with a slope, driveway, pool or foundation above, are engineered and often require much deeper or wider over-excavation than a simple base trench — plus a permit. Also have utilities located before you dig. This tool estimates typical base-trench excavation for planning and budgeting; it is not an engineered excavation or shoring design.

Practical excavation tips

Call before you dig. Have underground utilities marked (811 in the US) before any excavation — free, and the law in most places.
Cut a little extra depth, not width. It's cheaper to trim base stone to level than to fight a trench that's too shallow — but over-widening just multiplies the soil you haul.
Stage the spoil. Keep it off the trench edge so it doesn't cave back in, and separate any topsoil you want to keep from the subsoil you'll haul.
Weigh the dumpster math. For soil, a heavier-rated or dedicated dirt dumpster, or a dump-truck haul, usually beats stacking multiple light cans.

Frequently asked questions

How much dirt comes out of a retaining wall trench?

Length × trench width × trench depth for the base trench. A 40 ft wall with a 2 ft trench about 14 in deep is roughly 3.5 cubic yards in the ground, about 4.3 loose after swell. Enter your wall for its own figure.

What is soil swell?

Excavated soil expands because digging loosens the settled, compacted ground. It's usually 20–30% more volume, so plan haul volume above the in-ground figure. Swell adds volume but not weight.

Why do I need more than one dumpster for a little soil?

Dumpsters have weight limits — often about 2 tons on a small can. Soil is heavy, so a few cubic yards can exceed the limit even though it looks like it fits, meaning extra cans or overage fees.

Should I hire an excavator or dig by hand?

A short, low wall base trench is doable by hand; longer or deeper digs, hard or rocky soil, and reinforced walls are far faster with a mini-excavator. Set an excavation rate to compare, or leave it blank for a DIY dig.

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