How many cubic meters per hour does an excavator move? How to calculate productivity

The formula: four numbers

It's the standard method to estimate an excavator's output, for any brand. Two numbers come from the machine and the material; the other two only your site can give you.

1. Bucket capacity comes from the datasheet

Use the capacity of the bucket your machine actually carries, not another configuration's. In the catalog, according to Komatsu's datasheets, the PC130-8 carries 0.5 m³, the PC200-10M0 and PC210-10M0 1.0 m³, the PC220LC-8 1.2 m³, the PC300-8M2 1.96 m³ (SAE rated), the PC360-8M2 2.23 m³ and the PC390LC-8M0 2.4 m³ with the standard bucket or 1.7 m³ with the rock bucket.

That figure is heaped and depends on the rating standard (the bucket guide explains it): it's just the starting point.

2. The fill factor depends on the material

A 1 m³ bucket almost never digs out 1 m³. The site's bucket table uses these fill factors, which are the industry standard:

• Mud and saturated soil: 1.05 (it heaps).
• Common earth, sand and gravel: 1.0.
• Hard, compacted clay: 0.85.
• Well-fragmented rock: 0.7.
• Poorly fragmented rock: 0.45 — fills less than half.

3. Cycles per hour are measured with a stopwatch

The cycle is the time the machine takes to load, swing loaded, dump and come back. It's the number that moves the result the most and the only one not on any datasheet: it depends on the swing angle, the cut depth, where the truck stands, the material's hardness and the operator. That's why you measure it on your site instead of copying it from another.

Cycles per hour = 3,600 ÷ average cycle in seconds.

• Start the stopwatch when the bucket enters the material and stop it when it enters again.
• Time 20 to 30 cycles in a row and average them; a single one misleads.
• Measure the real job: the same depth, the same swing and the same truck you'll use.
• Log waits separately (a truck that doesn't arrive, repositioning the machine): they go into efficiency, not the cycle.

4. Efficiency: the minutes it really works

No machine works 60 minutes of every hour: truck waits, moves, operator changes and breaks eat part of the shift. Measure it like the cycle: watch for an hour and count the minutes the machine was digging and loading. If it was 45, your efficiency is 45 ÷ 60 = 0.75.

Telematics helps measure it across the whole shift. On Komatsu, KOMTRAX records real hours and idle time, and Komatsu's 3D guidance (3DMG) adds a payload meter that weighs what each bucket lifts, on excavators up to the PC490, according to Komatsu. In haul fleets, Smart Construction Fleet records each truck's cycle times.

5. Bank or loose cubic meters?

When dug, material swells: the same weight takes up more volume. The formula gives loose cubic meters, which is what the bucket and the truck carry. But the cut on the drawing and many contracts are measured in bank cubic meters, the ground in place. Mixing them up inflates output.

The conversion comes from densities: bank m³ = loose m³ × loose density ÷ bank density. With the densities from Komatsu's Specifications & Application Handbook used in the bucket table, rock goes from 2.8 t/m³ in the bank to 1.6 loose: each loose cubic meter of rock is only 0.57 bank m³. If your material isn't in the table, weigh it: fill the bucket, weigh the load and divide by the volume.

6. Worked example (with assumptions)

Illustrative example with assumptions, not a promise of output. Machine: Komatsu PC200-10M0, 1.0 m³ bucket according to its datasheet. Material: hard clay, fill factor 0.85, loose density 1.45 t/m³ and bank density 1.8 t/m³ (bucket table). Assume you timed 30 cycles and the average was 24 seconds, and that in the observed hour the machine worked 45 minutes.

Cycles per hour: 3,600 ÷ 24 = 150. Output: 1.0 × 0.85 × 150 × 0.75 = 95.6 loose m³ per hour. By weight: 95.6 × 1.45 = 138.7 t per hour. In bank terms: 138.7 ÷ 1.8 = 77.0 m³ per hour.

Now change a single figure: if the truck is badly placed and the cycle rises to 30 seconds, you get 120 cycles and 76.5 loose m³ per hour, 20% less with the same machine. That's why the cycle is measured and looked after.

7. How to raise output without changing machines

What improves output shortens the cycle or raises efficiency; going up a bucket size without checking stability is a mistake (the bucket guide explains it).

• Position the truck so the swing is short and dumping doesn't force extra lifting.
• Have the next truck ready: an excavator that waits has low efficiency even with a good cycle.
• Use the right bucket and teeth for the material: a bucket that doesn't penetrate lengthens every cycle.
• Train the operator: the group's APMT Academy runs the basic excavator course.
• Check idle time in KOMTRAX: engine hours without output lower efficiency and raise cost.

8. From m³ per hour to cost per m³ and to the fleet

Output per hour is half the math. Divide the machine's cost per hour by its output and you get the cost per cubic meter, which is what you quote a job with; the site's cost-per-hour calculator gives you a first figure. When the excavator loads trucks, its output also depends on how many trucks there are and how long they take to come back: with too few, it waits; with too many, they queue. A fleet study solves that: it measures your cycles and haul routes and compares alternatives by cost per tonne.

Grupo ConstruMarket is Komatsu's authorized distributor in El Salvador (Zaragoza, Antiguo Cuscatlán, San Miguel), Guatemala as CMARKET (Mixco, Río Hondo, Xela), Nicaragua (Managua) and Panama (Panama City), with excavators from the PC130-8 to the PC1250-11R in all four countries.