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Fill the bucket: material density
Short answer
A bucket isn't chosen by cubic metres but by what your material weighs. Load per pass = bucket × fill factor × loose density. The factory standard bucket is built for ~1.5 t/m³: on a PC200-10M0 CE (1 m³), wet sand and gravel loads 2.02 t per pass —135 % of what it takes— and topsoil just 0.95 t. Heavy material calls for a smaller bucket; light material, a bigger one.
The rule you're practising
- Load per pass = bucket capacity × fill factor × the material's loose density.
- The factory standard bucket is set up for ~1.5 t/m³ (common earth): on an excavator, what it takes per pass is its spec-sheet bucket × 1.5 t.
- On a skid steer the limit is its rated operating capacity, from the spec sheet.
- When dug, material swells: rock goes from 2.8 t/m³ in the bank to 1.6 loose (75 % more volume); each loose m³ is 0.57 bank m³.
- Heavy material → less bucket volume. Light material → more volume. And always: the limit is stability, not output.
Where each number comes from
- Loose and bank densities.Source: 'Weight data of materials' table in Komatsu's Specifications & Application Handbook; salt, scrap, wood chip and bagasse are general reference. The same bucket table on this site.
- Fill factors.Source: industry standard, from the site's bucket table.
- Each machine's bucket and rated capacity.Source: catalog spec sheets. A machine that doesn't publish its bucket is left out (Bobcat skid steers publish capacity, not the bucket).
- Bucket size and your material's weight.Source: you set them. The simulator only counts the material: a bigger bucket also weighs more.
FAQ
What is a material's density and why does it matter when choosing a bucket?
It's how much a cubic metre weighs. With the same bucket, a heavy material loads far more tonnes per pass than a light one: with 1 m³, wet sand and gravel loads 2.02 t and topsoil 0.95 t. That's why a bucket is chosen by weight, not volume.
What's the difference between bank and loose density?
Bank is the material in place; loose, once dug. Digging swells it and the same weight takes more volume: rock goes from 2.8 to 1.6 t/m³. Buckets and trucks carry loose material; many contracts pay bank m³.
How do I measure my material's density?
Fill a container of known volume level to the rim, weigh it and subtract the empty container. Kilos ÷ litres = tonnes per cubic metre. The simulator does it for you in 'Material not listed? Weigh it'.
Can I fit a bigger bucket on my excavator?
Only if the material is light and the machine can hold it sideways with the real material loaded. An oversized bucket with heavy material adds tipping risk, lowers penetration and speeds up pin and bushing wear.
Density and bucket tableGuide: how to choose the bucketNext: load the truckAll simulators