This guide is for site managers, planners and procurement teams who know the quantity of work and the deadline but still have to put a number on the request. It shows how to estimate equipment quantities for a construction project: how many loading machines, how many trucks behind each, and where the site stops extra machines from helping. The worked example uses made-up numbers. Replace them with your own.
Why decide the number of machines separately from the size?
A bigger machine and more machines both move more material, but they fail in different ways. Too few machines and the deadline slips. Too many and they block each other and wait for trucks, and depending on the hire terms you may still pay for idle time.
This guide covers the number. For the size of one excavator, read what size excavator you need. If different phases need different machines, estimate each phase on its own, as in planning equipment by construction phase.
What do you need to know before you can estimate?
You need five inputs. If one is missing, the estimate is a guess, so ask for it first.
- Quantity of work. For earthworks, this is volume in cubic metres, usually measured in the ground. Take it from the drawings or the bill of quantities, and check which basis the figure uses.
- Material. Sand, clay, rock and mixed fill all load and haul differently.
- Deadline. The number of working days you really have, not calendar days.
- Usable hours per day. Count hours the machine can actually work, after breaks, prayer times, fuelling, heat limits and site rules.
- Site limits. Access, working space, haul route and where the material goes.
Usable hours drive the result. Shorter shifts, summer hours or night work change the number of machines you need for the same deadline. If your project falls in Ramadan or summer, read planning machines around Ramadan and summer schedules.
How do you estimate equipment quantities from the work and the deadline?
A machine-day is one machine working one normal working day. Use three steps:
- Find the output of one machine per working day (output per hour × usable hours).
- Divide the quantity of work by that daily output. The answer is machine-days.
- Divide machine-days by the days available. Round up to a whole machine.
The weak point is step 1. A bucket size or a truck payload in a catalogue is a capacity. It is not output. Real output also depends on cycle time, material, operator skill and waiting, and is usually well below what the capacity suggests.
Watch out. Never use a catalogue capacity as an output figure. Ask the supplier what the machine realistically moves per hour on your material and conditions, and ask what that figure assumes.
Questions to ask the supplier:
- What output per working hour do you expect on this material, in these conditions?
- What does that figure assume about the operator, the haul distance and waiting time?
- Is the operator included, and how many hours per day are covered?
- What is the replacement time if this machine breaks down?
How many trucks does one excavator need?
An excavator or loader that waits for a truck produces nothing. A truck queue is also wasteful. The aim is a fleet where the loading machine never waits.
Use this rule: trucks needed ≈ truck round-trip time ÷ time to load one truck, rounded up. The round trip is the sum of loading, travel to the dump point, dumping and the return.
Two points make the count more accurate:
- Excavated soil takes more volume once it is loose than it did in the ground. Count truck loads in loose volume, so the number of loads is higher than the in-ground volume suggests.
- Time the haul at the hours you will really work, because traffic, queues and a long gate wait can all lengthen the round trip. Re-check the count once real round-trip times are known on site.
For truck types, see dump truck types: rigid, articulated and mining. To compare machines directly, browse dump trucks, excavators and loaders.
What spare capacity should you allow?
Plan for breakdowns, not for the perfect day. The right amount depends on how much one failure costs you.
| Task type | What a breakdown does | What to plan |
|---|---|---|
| On the critical path (everything waits for it) | Stops the whole chain | A standby machine, or a replacement time agreed in writing with the supplier |
| Has slack (other work can continue) | Delays only that task | Extra time in the schedule, or a replacement time from the supplier |
| Short job of a day or two | Loses a large share of the job | Book early and confirm a backup before you start |
Do not hide spare capacity inside optimistic output figures. Keep the estimate honest, then add the standby as a separate line.
Where does the site cap the number of machines?
More machines at one working face do not give more speed once the space and the safe working distances are used up. After that point, extra machines wait, crowd the area and add risk.
Check these before you add a machine:
- The width of the cut or the length of the face where machines can work side by side
- Safe distances between working machines, including their swing and travel areas, and between machines and people on foot
- One-way haul routes, turning space and a clear loading position for trucks
- Access gates and the dump point, which can become the bottleneck
If the layout allows only one working face, a faster result may need more working faces, a longer shift or a larger machine, not more machines on the same face. Requirements differ by project and site owner, so confirm the safe layout and traffic plan with the site team before adding machines or hours.
A worked example, step by step
This is an illustrative example. The numbers are made up to show the method; use your own.
Say you must dig 3,000 cubic metres in 5 working days. The supplier says one excavator realistically moves 30 cubic metres per working hour on this material. You can work 8 usable hours a day.
- Daily output of one machine: 30 × 8 = 240 cubic metres.
- Machine-days: 3,000 ÷ 240 = 12.5.
- Machines for 5 days: 12.5 ÷ 5 = 2.5, rounded up to 3 excavators.
Now the trucks. Say a truck takes 20 minutes to load at that rate, and its full round trip (load, travel, dump, return) is 60 minutes. These truck figures are simplified.
- Trucks per excavator: 60 ÷ 20 = 3.
- Three excavators would need 9 trucks, if the site can fit them.
If the site can fit only two excavators, the same maths gives 12.5 ÷ 2 = 6.25 days, so the deadline needs longer hours, more working faces or more days. That is the moment to talk to the site team, not after mobilising.
One common mistake shows why usable hours matter. If you assumed 12 hours a day instead of 8, output would be 360 cubic metres, 3,000 ÷ 360 = 8.3 machine-days, and the answer would drop to 2 excavators. If the site really delivers 8 hours, that plan misses the deadline.
How to do this on Maedah
Post one project request with the machines and quantities you worked out, the city and site on the map, the dates and any requirements such as driver or Urgent. Put the realistic output you expect and the shift hours in the notes, so suppliers quote against the same assumptions.
Suppliers that offer the category and serve your city send sealed quotes, shown side by side. Compare what each includes, the response time and the replacement arrangement. Start from the request form, and read what to write in an equipment rental request first.
