How to calculate the required equipment for work volume and deadlines: formulas and examples

Correct equipment selection is not about 'getting something more powerful just in case.' It is a balance between the volume of work, the deadline, and the machine-hour cost. A mistake hits from both sides: an underpowered fleet will not meet the schedule and will jeopardize the contract or lead to tender penalties, while an excessive one will freeze money in downtime and fuel. Below is a working methodology by which a procurement officer or foreman can estimate the required number and class of machines before even arriving at the site.

Basic logic: from volume to productivity

Any calculation starts with one simple formula:

Required productivity = Work volume ÷ Deadline

First, we reduce the volume to clear units (cubic meters of soil, tons of material, square meters of pavement), then convert the deadline into work shifts. For example, 12,000 m³ of soil needs to be excavated in 20 working days in one 8-hour shift. This means the required shift productivity is 600 m³/shift, or 75 m³/hour. This is the target for which the machine is selected.

The number of equipment units is calculated as follows:

N machines = Required productivity ÷ Productivity of one machine

The result is almost always rounded up and a reserve is added — more on this below.

Technical and operational productivity

A key mistake for beginners is taking the rated specification directly. In reality, a machine doesn't work 60 minutes per hour: refueling, repositioning, waiting for transport, and lunch breaks. Therefore, two indicators are distinguished.

• Technical performance — how much the machine outputs during continuous operation.
• Operational productivity — taking into account the time utilization factor (Kv), usually 0.7–0.85.

For earthmoving equipment, the calculation also includes the bucket fill factor (Кн ≈ 0.8–1.0) and the soil bulking factor (Кр ≈ 1.1–1.3). It is the operational figure that should be used in the selection formula.

Example 1: excavation work with an excavator

Let's take the same volume — 75 m³/hour of required productivity. An excavator with a 1.0 m³ bucket and a cycle time of 20 seconds gives 3600 ÷ 20 = 180 cycles per hour. Multiply by bucket volume and fill factor, divide by the swell factor: 180 × 1.0 × 0.9 ÷ 1.2 ≈ 135 m³/hour technical productivity. With a utilization factor of 0.75, we get about 100 m³/hour operational productivity.

Conclusion: one ~20-ton class machine covers the task, but with only a 25% margin. In rain and viscous soil, this may not be enough — you should either opt for a higher-class machine or schedule a second shift.

Example 2: synchronization with soil removal

An excavator is useless if dump trucks are not supplied for it. If it loads 100 м³/hour, and a dump truck with a volume of 15 м³ (loose) at a 5 km distance makes a trip in 30 minutes, that is 2 trips and 30 м³/hour per truck. To avoid creating a queue and keeping the excavator idle, 100 ÷ 30 ≈ 3–4 dump trucks are needed. The mismatch between 'earthmover and transport' is the most common reason for pace failure on site.

Example 3: roller compaction

For compaction, productivity is calculated by area and layer:

P = 1000 × V × (B − b) × h ÷ n

where V is speed (km/h), B is drum width (m), b is lane overlap (m), h is layer thickness (m), n is the number of passes. At V = 3 km/h, B = 2.1 m, b = 0.2 m, h = 0.3 m, and 6 passes, we get about 285 m³/h. This shows whether compaction is keeping up with the filling pace or if the roller is becoming a bottleneck.

Reserve and "bottlenecks"

Calculation by a pure formula represents ideal conditions. In practice, allow for:

• 10–15% reserve productivity for bad weather, maintenance, and minor breakdowns;
• replacement in critical operations — if the entire cycle depends on one machine, its stoppage stops the site;
• chain balance — the pace is set by the slowest link, not the most powerful one.

Pre-purchase checklist

• Reduce volume to units and divide the timeframe into shifts.
• Calculate the required hourly productivity.
• Determine the operational productivity of the machine with coefficients.
• Check the entire technological chain for synchronicity.
• Provide reserve and substitution for key operations.
• Consider soil type, climate, and site logistics.

This approach helps to buy exactly the fleet that pays off, rather than overpaying for extra tons or repairing overloaded equipment.

We will help you choose for your volume

If you already know the volume and deadlines but are unsure about the class and number of machines, specialists from the official FURD dealer in Kazakhstan will help calculate the configuration for your task and select models from the lineup. It is best to check the current price and delivery times directly with a manager. Leave a request on the website or message us on WhatsApp — we will analyze your site and offer the optimal solution.