A cubic metre is not a complete quantity description: name the material state and ratio basis before converting a compacted demand into bank and loose volumes.
Name the state of every quantity
Bank volume describes material in its original position, loose volume describes disturbed material, and compacted volume describes the specified placed condition. FHWA distinguishes these states and calls for project-specific geotechnical information. Its roadwork examples are not universal coefficients for a garden or house.
Keep the design quantity, measured excavation and supplier delivery record separate. Mark each number with material, state, units, date and source. A stockpile estimate or a vehicle’s nominal body volume is not automatically the compacted fill demand.
FHWA Earthwork Design: volume states and geotechnical basis (English; US roadwork context) ↗Confirm the two denominators before calculating
Here c = compacted volume / bank volume and l = loose volume / bank volume. Both must describe compatible material and the same bank basis. Ask the designer or supplier to spell out a factor stated only as “shrink”, “swell” or “balance”: another document may use a reciprocal or include different losses.
A volume ratio is not a percentage of maximum dry density or proof of compaction acceptance. Do not enter a field density target such as 95% as c = 0.95. Check moisture/material scope and whether handling losses are already included; the calculator cannot reconcile incompatible records or select the factors.
FHWA CFLHD Earthwork Representation: factor definitions and geotechnical recommendations (English PDF; not household design values) ↗Convert the target without adding percentages
Fictional C = 9 m³, c = 0.90 and l = 1.25 give B = 9 / 0.90 = 10 m³ bank and L = 10 × 1.25 = 12.5 m³ loose. The loose/compacted multiplier is 1.25 / 0.90 = 1.388889. These values are arithmetic inputs, not a recommendation for a named soil.
Do not simply add a 25% loose increase and a 10% compacted reduction: 9 × 1.35 = 12.15 m³, not 12.5 m³. A factor above one for compacted/bank is not rejected automatically: FHWA describes materials such as rock that can remain larger than their original bank volume. The actual factor still needs evidence.
Keep procurement and safe execution separate
Before any order, confirm the supplier’s state of measurement, material suitability, specification and documented allowances. This calculator adds no hidden waste and does not convert volume into tonnes or vehicle payload. A change of material or moisture scope needs matching new data, not reuse of convenient coefficients.
This is quantity accounting, not permission to excavate, enter a trench or choose a safe side slope. It does not set lift thickness, equipment, compaction energy, testing or density acceptance. Keep those decisions with the appropriate project professionals and the applicable local process.
Keep the quantity basis visible
| Record | Meaning here | Do not substitute |
|---|---|---|
| C, compacted m³ | Specified final placed volume | Loose pile or truck body |
| B, bank m³ | Original-position volume basis | Delivered loose cubic metres |
| L, loose m³ | Disturbed volume on the stated basis | Tonnes or allowable payload |
| c and l | Vc/Vb and Vl/Vb, documented together | Density acceptance or unnamed reciprocal |
Worked example
Fictional factors, not a soil recommendation
A reviewed compacted target is 9 m³. For the example only, compatible reported volume ratios are c = 0.90 and l = 1.25; no extra reserve is added.
B = 9 / 0.90 = 10 m³ L = 10 × 1.25 = 12.500 m³ L / C = 1.25 / 0.90 = 1.388889 ×
The example requires 10 m³ on the bank basis and 12.5 m³ on the loose basis. Confirm the actual factor definitions and supplier measurement basis before using any quantity for an order.
What to have ready
- Compacted demand and material specification identified
- Both volume-ratio definitions and sources recorded
- Same bank denominator and compatible conditions
- Included losses and any separate allowance documented
- Supplier measurement state and professional checks confirmed
Common mistakes
- Treating bank, loose and compacted cubic metres as interchangeable.
- Entering a density test target as a volume ratio.
- Adding shrink and swell percentages with different denominators.
- Reusing factors from another material or moisture basis.
- Turning this quantity into permission for excavation or compaction.
Use and limitations. Sources include US public agencies. Principles are general; regulations and design values must be checked where you live.Worked examples use stated hypothetical inputs.