Ask ten supervisors how much an excavator produces in an hour and you will get ten different answers. One will quote the brochure. Another will say "about 30 dumper loads, sir". A third will point at the production register and shrug. They can all be right, because the real figure depends on the bucket, the material, the operator, the digging face and even the weather.
Still, every mine and quarry needs a number to plan with. How many dumpers should be matched to this machine? Will the shift target be met? What is the cost per tonne? This guide shows how to calculate the hourly production of an excavator, whether it is a Komatsu PC200, PC300, PC450 or any other make, using a method you can check against your own site data.
A quick note on the name: "PC" is the model prefix Komatsu uses for its hydraulic excavators, and in Indian mines the term is often used for any excavator. The calculation below works the same way for Hitachi, CAT, Volvo, Tata Hitachi and others.
The idea in one line
An excavator's hourly production is simply: how much material one bucket carries, multiplied by how many buckets you load in an hour, adjusted for the fact that no machine works at full speed for a full 60 minutes.
The inputs you need
Bucket capacity (m³): the heaped capacity of the bucket fitted on the machine. Do not assume the standard bucket is on the machine; many mines run heavy-duty or rock buckets with a different capacity. Check the plate or the manufacturer's data.
Fill factor: how full the bucket really gets. Loose, free-flowing material fills it well. Poorly blasted boulders leave gaps and bring the number down.
Cycle time (seconds): the time for one full loop of dig, swing to the truck, dump and swing back. Measure this with a stopwatch on at least 15 to 20 cycles and take the average.
Job efficiency: the fraction of each hour the machine is actually working. A common assumption is 50 minutes per hour, which is 0.83. On a poorly run site it can be much lower.
Swell factor or load factor: broken rock takes up more space than rock in the ground. If you want production in bank cubic metres (BCM), you need to convert from loose cubic metres (LCM).
Density: to convert volume into tonnes. Use loose density for loose volume and in-situ density for bank volume.
The formulas
| Step | Formula |
|---|---|
| Cycles per hour | 3600 ÷ cycle time (seconds) |
| Theoretical production (LCM/hr) | Bucket capacity × fill factor × cycles per hour |
| Actual production (LCM/hr) | Theoretical production × job efficiency |
| Load factor | 1 ÷ (1 + swell %) |
| Production in bank volume (BCM/hr) | Actual LCM/hr × load factor |
| Production in tonnes per hour | LCM/hr × loose density, or BCM/hr × in-situ density |
For example, 30% swell gives a load factor of 1 ÷ 1.30 = 0.77.
Worked example 1: Mid-size excavator in overburden
Imagine a PC300 class machine removing overburden in an open cast mine.
Given data
- Bucket capacity = 1.6 m³
- Fill factor = 0.90
- Cycle time = 22 seconds
- Job efficiency = 50 min per hour (0.83)
- Swell = 30% (load factor 0.77)
- In-situ density of overburden = 2.2 t/m³
Calculation
Cycles per hour = 3600 ÷ 22 = 163.6
Theoretical production = 1.6 × 0.90 × 163.6 = 235.6 LCM/hr
Actual production = 235.6 × 0.83 = 196.4 LCM/hr
In bank volume = 196.4 × 0.77 = 151.2 BCM/hr
In tonnes = 151.2 × 2.2 = about 333 tonnes per hour
Worked example 2: Large excavator loading blasted iron ore
Given data
- Bucket capacity = 2.5 m³
- Fill factor = 0.85
- Cycle time = 26 seconds
- Job efficiency = 48 min per hour (0.80)
- Loose density of blasted ore = 2.4 t/m³
Calculation
Cycles per hour = 3600 ÷ 26 = 138.5
Theoretical production = 2.5 × 0.85 × 138.5 = 294.2 LCM/hr
Actual production = 294.2 × 0.80 = 235.4 LCM/hr
In tonnes = 235.4 × 2.4 = about 565 tonnes per hour
Over an 8-hour shift that is roughly 4,520 tonnes if the machine works the full shift. If mechanical availability is 85%, expect closer to 3,840 tonnes.
How many dumpers does this excavator need?
This is where the calculation earns its keep. Continuing with Example 2:
- Payload per bucket = 2.5 × 0.85 × 2.4 = 5.1 tonnes
- Dumper capacity = 40 tonnes, so passes to fill one dumper = 40 ÷ 5.1 ≈ 8 passes
- Loading time = 8 × 26 s ≈ 3.5 minutes per dumper
- Assume a full dumper cycle (load, haul, dump, return, spot) of 30 minutes. With 50 productive minutes per hour, one dumper makes about 1.67 trips per hour, which is about 67 tonnes per hour
- Dumpers needed = 565 ÷ 67 ≈ 8.5, so plan for 9 dumpers
With fewer than that, the excavator waits for trucks. With many more, trucks queue at the face and you burn diesel for nothing. Remember that haul distance changes the dumper cycle time, so redo this whenever the haul route changes.
Typical values to start with
These are indicative ranges only. Always replace them with figures measured at your site.
| Item | Indicative range | Comment |
|---|---|---|
| Fill factor | 0.60 to 1.0 | Lower for poor fragmentation and boulders, higher for loose material |
| Cycle time | 18 to 30 seconds | Depends on machine size, swing angle and digging depth |
| Job efficiency | 0.70 to 0.85 | 45 to 50 min per hour is a common planning value |
| Swell | 10% to 50% | Low for sand and gravel, higher for clay and blasted rock |
What pulls hourly production down
- Poor blasting. Oversize boulders and tight muck piles slow every cycle and lower the fill factor.
- Wrong bench height. Too low and the machine keeps repositioning, too high and it is unsafe and the muck pile can hang up.
- Large swing angle. If the dumper is parked far around from the digging face, the cycle time rises.
- Truck waiting time. A perfectly good excavator still loses hours if the dumpers do not arrive on time.
- Poor floor and haul road. Soft or wet floors slow travel and make loading harder.
- Operator skill. A good operator can beat an average one by a noticeable margin on the same machine.
- Breakdowns and slow maintenance. Availability is a big hidden factor.
- Monsoon, dust and night shifts. They all show up in the numbers.
Common mistakes
- Using the brochure's maximum bucket capacity without checking the fitted bucket.
- Forgetting the fill factor, which overestimates output.
- Mixing bank and loose volumes, so the swell is either missing or counted twice.
- Using a guessed cycle time instead of a measured one.
- Assuming 60 working minutes in an hour.
- Multiplying by 8 or 12 hours without considering shift change, breakdowns and waiting.
- Ignoring dumper availability when estimating what the excavator will actually load.
How to check your calculation on site
Do not trust a spreadsheet blindly. Cross-check it:
- Count the dumper loads the excavator filled in a full hour or full shift.
- Multiply by the average payload, and compare with weighbridge records where possible.
- Time at least 20 cycles and recompute the cycle time.
- If the gap between calculated and actual is more than about 10 to 15%, look for the reason. It is usually fill factor, waiting time or density.
Frequently asked questions
Does "PC" only mean Komatsu?
Strictly yes, PC is Komatsu's model prefix, but in everyday mining talk people use it for any hydraulic excavator. The formula does not depend on the brand.
Should I calculate in LCM, BCM or tonnes?
Whatever your planning and reporting is based on. Pit design usually uses BCM, while loading and dispatch use tonnes. Just convert carefully, using the right density and swell for each.
What is a realistic hourly production for a PC200?
It depends heavily on bucket size, material and cycle time, so there is no single answer. Calculate it with the steps above using your own measured values, and then verify against dumper counts.
Why is my actual output lower than the calculation?
Usually because of optimistic job efficiency, a fill factor that is too high, or time lost waiting for dumpers. Check those three first.
Final thoughts
The formula itself is simple. What makes a calculation useful is the quality of the inputs: a measured cycle time, a realistic fill factor, the right density and an honest efficiency figure. Spend an hour with a stopwatch at the face and you will have better data than most spreadsheets ever see.
If you would like an Excel sheet for excavator and dumper matching, or similar examples for specific machines and minerals, write to me in the comments and I will cover it in a follow-up post.
 Production Calculation per Hour: A Practical Guide for Indian Mines and Quarries || Indian Minerology ){kind=link}
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