Bucket Capacity & Fill Factors
The three layers of honest loading math: the rating standards (with the 1:1-vs-2:1 heap correction), typical bucket sizes by machine class, and the fill factors by material. Everything below the standards row is estimate-only — four published value-sets disagree at the edges, and the spans show it. Loader fill factors run on a different heap basis (2:1) and digging action — never mix the two tables.
Excavator GP bucket sizes by class
| Machine class | GP bucket (CY) | Typical |
|---|---|---|
| Mini (1–3.5 t) | 0.02–0.12 | ~0.05 |
| Compact (3–8 t) | 0.1–0.35 | ~0.2 |
| Mid (12–16 t) | 0.4–0.8 | ~0.6 |
| 20-ton class | 1.0–1.6 | ~1.25 |
| 30–35 t | 1.5–2.25 (mass-ex to 2.5) | ~2 |
| 45 t + | 2.5–6.5 | ~3–4 |
Excavator fill factors by material
| Material | Fill factor (of heaped rating) | Note |
|---|---|---|
| Moist loam / sandy clay | 100–110% (some sources to 120) | — |
| Sand & gravel, loose | 90–110%, typical ~100% | Sources spread widest here among soils |
| Common earth / topsoil | 80–110% | — |
| Hard, tough clay | 65–95%, typical 80–90% | Textbook sets run lower than mfr sets |
| Wet clay | 50–90% — varies widely | The widest spread in print; test your dirt |
| Rock, well blasted | 60–80%, typical ~70% | — |
| Rock, poorly blasted | 40–60% | — |
From bucket to bid
Production chains multiply, so errors compound: an optimistic fill factor times an optimistic cycle count times a 60-minute hour is how a bid loses money by lunch. The sober chain — lcy/hr = heaped bucket cy × fill factor × cycles per hour × job efficiency — feeds the truck math on the truck capacity chart and converts through the swell factors to the bank yards the contract pays on.
Common questions
What is the difference between struck and heaped bucket capacity?
Struck is leveled at the strike-off plane; heaped adds the pile above it — and the pile's shape is standardized: sae j296 / iso 7451 — heaped at 1:1 (45°) repose, while sae j742 — heaped at 2:1 repose. That basis difference (commonly stated backwards) is why loader and excavator numbers never share a table, and why spec sheets always quote heaped.
What is a bucket fill factor?
The fraction of the heaped rating the bucket actually captures per pass — over 100% for moist cohesive soils that heap above the rating, down to 40–60% for poorly blasted rock. Published sets genuinely disagree at the edges (wet clay spans 50–90% across four sources), which is why this chart prints the spans: pick from your own dirt, not the optimistic column.
How do you estimate excavator production?
LCY/hr = heaped bucket CY × fill factor × cycles per hour × job efficiency. Efficiency is the honest term: 50-min hour = 0.83 (well-run job); 45-min = 0.75 (average); 40-min = 0.67 (difficult). The result is loose yards — divide loose output by (1 + swell) for bank cy/hr — and a 20-ton machine with a 1.25 CY bucket at 90% fill, 150 cycles and a 50-minute hour moves ~140 LCY/hr in easy digging. Halve it before you bid it.
Run your whole job on the same numbers
These NORDIX tools are a taste of the full platform — bid pipeline, estimating, and job costing that carry your numbers from the first bid to the final invoice. Our team sets it up for your shop and walks you through your next real job.
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