Sample inputs and expected sizing
Use this example to sanity-check your settings before field validation.
| Parameter | Example value | Notes |
|---|---|---|
| Total quantity (bank) | 2,500 m³ | Earthworks over 20 working days |
| Swell factor | 20% | Loose volume increases for hauling |
| Truck body capacity | 12 m³ | Loose capacity, consistent definition |
| Fill factor | 95% | Underfill and load control allowance |
| Cycle time | 25 min | Includes load, travel, dump, and turns |
| Working hours | 10 h/day | Planned shift hours |
| Utilization | 85% | Breaks and minor delays included |
| Availability | 90% | Expected in-service portion of fleet |
| Queue factor | 10% | Congestion adjustment |
| Spare trucks | 10% | Added for resiliency |
Core sizing relationships
1) Loose demand: Daily loose volume = Daily bank volume × (1 + Swell%).
2) Effective payload: Effective truck capacity = Body capacity × Fill factor%.
3) Effective cycle time: Teff = Tcycle × (1 + Queue%).
4) Effective working time: Weff = (Hours × 60) × Utilization%.
5) Trips per truck: Trips = Weff / Teff.
6) Production per truck: P = Trips × Effective capacity.
7) Fleet size: Trucks = Demand / (P × Availability%). Round up to a whole truck, then add spares.
A field-ready workflow
- Pick demand basis: total over days, or a daily target.
- Select units: cubic meters or tons, then set density if needed.
- Enter truck capacity and a realistic fill factor.
- Choose cycle input: direct cycle time, or compute from distance.
- Set utilization, availability, and queue factor conservatively.
- Click Calculate Fleet and review the breakdown.
- Validate on site: track real cycle time and adjust.
Truck Fleet Sizing for Reliable Production
1) Why fleet sizing matters on earthmoving projects
Haulage often controls daily output on excavation and disposal work. An undersized fleet starves the loader and misses targets, while an oversized fleet creates queues, fuel burn, and higher standby cost. Good sizing balances daily demand against realistic trips per truck. Right-sized fleets also reduce fuel, tire wear, and rehandling.
2) Demand, swell, and unit conversions
Planning quantities are usually bank volume (in-situ) or tons from tickets. For hauling, the relevant demand is loose volume because material expands after digging. Swell can be about 10–30% depending on soil or rock. If you enter tons, density converts tonnage to volume before swell is applied.
3) Cycle time is the strongest driver
Cycle time includes loading, travel, dumping, and maneuvering. Small increases reduce trips quickly. With 10 planned hours and 85% utilization, effective time is 510 minutes. At an effective cycle of 25 minutes, one truck makes about 20 trips; at 30 minutes, it falls to about 17 trips. Measure cycle parts and use averages, not best cases.
4) Utilization, availability, and standby allowances
Utilization covers operational losses such as breaks, refueling, traffic control, and minor delays. Availability is the portion of trucks mechanically ready to work. A queue/standby factor inflates cycle time to reflect waiting at the loader or dump point, especially on narrow haul roads. On busy sites, standby can exceed 20%, so track it and improve flow with staging, radio discipline, and clear right-of-way rules.
5) Spares and continuous improvement
Spares protect production when trucks fail or are reassigned. Many sites start with 5–15% spares based on fleet age and support. After mobilization, record payload accuracy, average speed, and queue duration for a week. Update inputs and re-size; modest improvements in cycle time or fill factor can reduce trucks while maintaining the target.
Frequently Asked Questions
1) Should I use bank volume or loose volume?
Use bank volume for estimating quantity in place, then apply swell to reach loose volume for hauling. Truck bodies are rated in loose capacity, so loose volume is the sizing basis.
2) What fill factor should I enter?
Start with 85–100% depending on loading control, material type, and spillage risk. Verify with scale tickets or measured truck counts, then refine the fill factor to match reality.
3) How do I estimate cycle time if I lack data?
Use the computed option with realistic speed, plus loading, dumping, and turning delays. After the first working day, replace estimates with observed averages from a time study.
4) Why add a queue or standby factor?
It covers waiting at the loader, traffic control, dump line-ups, and road congestion. Without it, the plan often underestimates trucks needed to reliably meet the daily target.
5) How do utilization and availability differ?
Utilization is operational time efficiency within the shift. Availability is the portion of trucks mechanically ready to work. Both reduce effective production and should be set conservatively.
6) When should I add spare trucks?
Add spares when breakdown risk is high, haul roads are rough, or reliability is critical. Typical spare planning is 5–15%, but older fleets or remote sites may require more.
7) Can this calculator size fleets for multiple loaders?
Yes, by splitting demand per loading unit and running separate scenarios. Each loader may have different cycle characteristics, queue behavior, and dispatch rules, so evaluate them independently.