Fill Volume Calculator
Order too little fill and the job stalls with the last corner still low; order too much and you pay to haul the surplus away. This calculator takes the length, width and fill depth of a rectangular or square area, all in metres, and returns the volume to fill it in cubic metres and litres. It fits the everyday jobs: raised beds and planters, trench backfill, slab bases, pond and pool surrounds, and levelling a yard one layer at a time.
This is the exact geometric volume of the space. It includes no allowance for compaction, settling or spillage, so order extra material on top of it for soil, sand or aggregate.
Quick Answer
A rectangular flower bed 4 m long, 2.5 m wide and 0.3 m deep needs 3.00 m³ of fill, which is 3,000 litres. That is the calculator’s pre-filled example: change any of the three measurements and the volume updates from the same formula, length × width × depth, with litres at exactly 1,000 per cubic metre.
Key takeaways
- Three measurements in metres are all this tool needs. It is a rectangular-prism calculation, so circles, triangles and slopes need the sectioning approach described below.
- The litres figure is not a second calculation: 1 m³ is exactly 1,000 litres by definition, which makes the litres line the handiest one for bagged material sold by the litre.
- The result is the empty space, not the delivery ticket. Loose fill settles and compacts after placement, so the order quantity belongs above the tool’s figure, never below it.
- Depth errors hurt most. A 5 cm depth mistake on a 10 m² area is half a cubic metre of material, while a 5 cm length mistake at 0.3 m depth adds far less.
- Quick Answer
- How to use the fill volume calculator
- The fill volume formula
- Worked example: the flower bed, checked step by step
- Converting the result: yards, cubic feet and bags
- Compaction and settling: the volume the tool does not add
- What competing calculators miss
- Frequently asked questions
- Add This Calculator to Your Website
- References
How to use the fill volume calculator
Measure the space in metres, type the three numbers in, and click Calculate. The result appears as cubic metres to two decimal places with the litres alongside it.
- Measure the length and width: run a tape along the two ground dimensions of the area. If you are planning the plot itself rather than filling it, the field area calculator works through the ground area on its own before depth enters the picture.
- Measure the fill depth: push a stake or ruler into the lowest point and mark the finished level you want. On uneven ground, take three to five depth readings across the area and average them.
- Convert before you type: the fields accept metres only. Feet convert at × 0.3048, inches at × 0.0254 and centimetres at ÷ 100, so a 6 inch layer is 0.1524 m, usually entered as 0.15.
- Read both numbers: cubic metres is the unit bulk suppliers deliver by; litres is the unit bags are labelled with. The badge under the result also restates the volume in cubic yards for suppliers who sell by the yard.
Zero, negative or blank entries return “Please enter valid positive numbers.” rather than a zero volume. That is deliberate: a silent 0.00 m³ on an order sheet reads like a real answer, and it never is.
The fill volume formula
Fill volume = length × width × depth. The three sides of a rectangular box multiplied together give its volume, and because every side here is in metres, the answer falls out in cubic metres with no conversion step inside the tool.
Volume (litres) = Volume (m³) × 1,000
The litres step is exact, not rounded. The litre is a special name for the cubic decimetre in the SI system, so a cubic metre, which holds 1,000 cubic decimetres, holds exactly 1,000 litres, as set out on the NIST SI units page for volume. The tool shows litres with thousands separators and no forced decimals, which is why a fractional result such as 3,125 litres appears whole while the cubic metre figure beside it reads 3.13 m³ after rounding to two places.
Worked example: the flower bed, checked step by step
The pre-filled example is a rectangular flower bed: 4 m × 2.5 m × 0.3 m. The base area is 4 × 2.5 = 10 m², and filling that base to 0.3 m gives 10 × 0.3 = 3.00 m³, or 3,000 litres.
Five more runs of this exact calculator are tabulated below. Each row was produced by the tool itself, so you can type any row in and get the same line back, including the rounding on the last row, where 3.125 m³ displays as 3.13 m³ while the litres stay exact at 3,125.
| Job | Length (m) | Width (m) | Depth (m) | Tool result |
|---|---|---|---|---|
| Flower bed (worked example) | 4 | 2.5 | 0.3 | 3.00 m³ (3,000 liters) |
| Trench backfill | 10 | 5 | 2 | 100.00 m³ (100,000 liters) |
| Single cubic metre pit | 1 | 1 | 1 | 1.00 m³ (1,000 liters) |
| Yard levelling layer | 6 | 4 | 0.15 | 3.60 m³ (3,600 liters) |
| Square planter, half a metre deep | 2.5 | 2.5 | 0.5 | 3.13 m³ (3,125 liters) |
| Site pad, large | 50 | 20 | 1.5 | 1500.00 m³ (1,500,000 liters) |
Converting the result: yards, cubic feet and bags
The tool reports cubic metres and litres only. The hand conversions below cover the units suppliers actually quote in, and each one starts from the tool’s cubic metre figure.
| You need | From the m³ result | Worked example (3.00 m³) |
|---|---|---|
| Litres (shown by the tool) | × 1,000 | 3,000 litres |
| Cubic yards | × 1.30795 | 3.92 yd³ |
| Cubic feet | × 35.3147 | 105.94 ft³ |
| US gallons (liquid fill) | × 264.172 | 792.52 gal |
| 40-litre bags | Litres ÷ 40, rounded up | 75 bags |
Two neighbouring jobs use the same multiplication with different stakes. A slab pour prices off the identical box volume, which is what the concrete volume calculator is built around, while loose material ordered by weight or by the loose yard belongs with the dirt calculator. Once the fill is priced as a dig-and-fill operation rather than a material quantity, the excavation cost calculator takes the same dimensions and attaches soil factors, hauling and permit fees to them.
Compaction and settling: the volume the tool does not add
The calculator returns the volume of the hole, not the volume on the delivery truck. Soil and aggregate arrive loose, full of air gaps, and rolling, tamping or simply wetting them squeezes that air out, so the placed layer ends up thinner than the loose volume you paid for.
Soil science measures this through bulk density, the dry weight of soil per unit volume, which rises as pore space falls. South Dakota State University Extension’s guide to bulk density as a soil health indicator tabulates ideal and root-restricting densities by texture, and Oklahoma State University Extension’s basics of soil bulk density explains how porosity and density move in opposite directions. In ordering terms, the practical response is simple: treat the tool’s figure as the finished, in-place volume and add a settling allowance before ordering, commonly 10 to 15 percent for soil that will be compacted in layers, less for coarse gravel that barely settles. On the worked example, a 10 percent allowance lifts the order from 3.00 m³ to 3.30 m³, and it is far cheaper to spread a small surplus thin than to pay a second delivery fee for a shortfall.
One safety point belongs with any fill that starts as a dig: excavating and backfilling near buried services is where volume jobs go wrong. The Hawaii Public Utilities Commission’s safe digging guidance sets out the US pattern, call 811 a few business days ahead and let the utilities mark their lines before any digging starts.
What competing calculators miss
Tools under this exact name split into three camps, and the gaps are consistent:
- Circular-only tools (Calculator Ultra’s fill volume page): the formula there is π × radius² × depth, a cylinder. Type a rectangular bed into that mental model and there is no length or width to enter at all. A gardener with a 4 m × 2.5 m bed is simply not served.
- Same-formula metric tools (Brave Calculator’s fill volume page): length × width × depth in metres, but the answer stops at cubic metres. No litres line, so anyone buying bagged material still has a conversion to do by hand, and no worked checks to validate the result against.
- US dirt and cubic-yard tools (the yard-based fill dirt calculators): feet and inches in, cubic yards, tons and cost out. Useful in the US, but a metric user has to convert every measurement before starting, and the built-in compaction and density assumptions are folded into the answer where you cannot see or remove them.
- Shipping CBM tools: multi-box freight volume with quantity multipliers and container fit. Accurate arithmetic aimed at cartons, not at a hole in the ground, and the depth question a fill job turns on is never asked.
- The gap this page fills: the rectangular case in pure metric, metres in and cubic metres plus exact litres out in one line, a checks table of real runs you can reproduce, and the compaction allowance handled honestly in the text instead of being baked silently into the number.
Frequently asked questions
It calculates the volume of a rectangular or square area from three measurements in metres: length, width and fill depth. The result is shown in cubic metres to two decimal places, with the same volume in litres alongside it.
Volume = length × width × depth, with every measurement in metres, which gives the answer in cubic metres. Litres = cubic metres × 1,000, because one cubic metre holds exactly 1,000 litres.
Not directly. The tool works in metres only, so convert first: multiply feet by 0.3048 and inches by 0.0254 to get metres. A 10 ft length, for example, is 3.048 m.
Measure the depth at several points and enter the average, or split the area into rectangular sections, run each section through the calculator, and add the results together. Averaging works well for gentle slopes; sectioning is safer for stepped or terraced ground.
No. It returns the exact geometric volume of the space, with no allowance for compaction, settling or spillage. Loose soil and aggregate settle once placed and compacted, so order extra on top of the figure the tool gives you.
No. It multiplies length by width, so it only describes rectangles and squares. For a round area, work out π × radius² × depth by hand, or inscribe the circle in a square, calculate the square, and treat the result as an upper estimate.
Divide the litres figure by the litres printed on the bag. The worked example gives 3,000 litres, so at 40 litres per bag you would need 75 bags. Round up to whole bags, and add your settling allowance before you divide.
A fill with zero or negative length, width or depth has no volume to calculate, so the tool asks for valid positive numbers instead of returning a misleading zero. Check for a missed field or a minus sign if you see that message.
Add This Calculator to Your Website
Embed this calculator on your own site with the code below. Pick a size to preview it live, then copy the code.
Powered by Calculator Zilo
References
- National Institute of Standards and Technology. SI Units: Volume. Accessed October 21, 2026.
- Bureau International des Poids et Mesures (BIPM). The International System of Units (SI Brochure). Accessed October 21, 2026.
- South Dakota State University Extension. Bulk Density is an Indicator of Soil Health. Accessed October 21, 2026.
- Oklahoma State University Extension. Basics of Soil Bulk Density. Accessed October 21, 2026.
- Soil Health Nexus (USDA NRCS partner resource index). Bulk Density: Soil Physical Properties. Accessed October 21, 2026.
- Hawaii Public Utilities Commission. Safe Digging Starts with Calling 811. Accessed October 21, 2026.