Fleet sizing: the calculation in 7 steps

Have you ever felt that your fleet is either overloaded or has vehicles standing idle unnecessarily? This is one of the most common challenges in transport management: fleet sizing!

In practice, this means having enough vehicles to meet demand without generating unnecessary costs. Correctly sizing a fleet can make the difference between an efficient, profitable operation and one that loses money every day through invisible waste.

So, how do you find the right balance? That is what you will see now:

• What is fleet sizing?
• Why is fleet sizing necessary?
• How do you size a fleet?
• What data are needed for fleet sizing?
• How do you calculate fleet size?
• How do you calculate fleet availability?
• How do you control a fleet?

What is fleet sizing?

Fleet sizing is the strategic planning that defines how many vehicles and which vehicle types are needed to meet a transport operation's logistics demands.

This process involves analyzing transport volume, delivery frequency, distances traveled and vehicle availability.

Why is fleet sizing necessary?

Proper fleet sizing is a matter of both savings and operational efficiency. When the fleet is well sized, vehicles are used intelligently, fewer resources are wasted and the company can serve its customers better.

A poorly planned fleet can generate hidden costs (also known as “invisible” costs).

If there are too many vehicles, the manager pays maintenance, insurance and depreciation on unnecessary assets. If there are too few, the company may face delays, driver overload and operational failures.

Another essential factor is predictability. With well-structured sizing, the manager can forecast costs more accurately, expand the truck fleet, plan vehicle replacements and optimize resource allocation.

How do you size a fleet?

To size a fleet, you need to analyze real data from the operation, such as delivery numbers, transported volume, routes traveled and peak demand periods. With this information and the right calculations, it is possible to identify whether the current fleet meets requirements or needs adjustment.

It is also important to consider cargo type, average trip time and delivery frequency. Some operations may need more agile vehicles for short distances, while others require large trucks for long trips.

In other words, fleet sizing depends directly on the nature of the business and the logistics strategy adopted.

What data are needed for fleet sizing?

The first step in sizing your fleet is collecting accurate data about fleet vehicles, the cargo to be transported and the transport operation's logistics.

In the example presented here, we consider a heavy-vehicle fleet, but with a few small changes you can adapt it to any vehicle type.

Below you will find all the variables you need to keep an eye on:

Vehicle data

• Chassis weight
• Trailer weight
• Gross vehicle weight
• Weight of other equipment (this includes trailer weight, equipment needed for loading and unloading, the fuel tank and other variables)

Cargo data

• Cargo type
• Cargo weight
• Quantity of cargo to transport

Transport operation data

• Unloading time – UT
• Loading time – LT
• Outbound trip route distance – OD
• Return trip route distance – RD
• Working hours – WH
• Working days (WD)
• Days stopped for maintenance (MD)

Use technology to help optimize sizing

Fleet management and telemetry software help keep track of indicators such as mileage traveled, fuel consumption and idle time, providing accurate data for sizing adjustments.

How to calculate fleet size in 7 steps

The fleet sizing calculation does not follow a single formula. To obtain an accurate result, you need to go through seven essential steps, considering everything from vehicle tare weight to the number of trips made per month. Each step helps find the best configuration for your operation. Take a look:

• Calculate vehicle tare weight
• Calculate transportable payload capacity
• Calculate the number of monthly trips needed
• Calculate total trip time
• Calculate the number of trips a vehicle makes per day
• Calculate the number of trips a vehicle makes per month
• Calculate the number of vehicles needed for the operation

But do not worry! In the next sections, we will detail each step and share practical tips to ensure efficient, accurate sizing. Ready?

1. Calculate vehicle tare weight

A truck's tare weight is the weight of the empty vehicle, without cargo. This value includes the structure, fixed equipment and fuel needed for the operation. It is fundamental to the fleet sizing calculation, as it directly influences gross vehicle weight and transportable payload capacity.

The calculation is simple: add chassis weight, trailer weight and the full fuel tank's weight, along with other fixed equipment.

The formula is:

With this information, you can move on to the next steps in the fleet sizing calculation.

2. Calculate transportable payload capacity

In the fleet sizing calculation, using only total load capacity as a reference can be a mistake. This can lead to excess weight, causing premature tire wear and increasing the risk of mechanical failures.

What really matters is payload, that is, the amount of weight the vehicle can carry without exceeding legal limits or wasting capacity. The calculation is simple: subtract the truck's tare weight from gross vehicle weight.

The formula is:

3. Calculate the number of monthly trips needed

Determining the number of monthly trips needed is essential to meet demand without creating idle time or overloading the operation. This balance ensures more efficient fleet use and reduces unnecessary costs.

To calculate it, divide the total quantity of cargo to transport (D) by the vehicle's payload capacity (L), which we determined earlier.

The formula is:

This calculation allows strategic operational planning, ensuring productivity and avoiding waste.

4. Calculate total trip time

In the fleet sizing calculation, determining total trip time is fundamental. First, we need to calculate outbound and return times.

The process is simple: divide the outbound or return trip distance by the truck's operational speed and multiply the result by 60 to convert to minutes.

The formulas are:

After obtaining these values, add them and include loading and unloading time to reach total trip time:

Tip: always work with time in minutes to avoid fractional numbers and make calculations easier.

5. Calculate the number of trips a vehicle makes per day

We are nearly there! Now that you have total trip time, the next step in the fleet sizing calculation is finding how many trips a vehicle can make in a day.

The calculation is simple: divide daily operating time (working hours) by total trip time.

The formula is:

Attention! If the result is a fractional number, do not worry. We will make the final adjustment in the next step.

6. Calculate the number of trips a vehicle makes per month

To complete this step in the fleet sizing calculation, first determine how many days a vehicle operates per month. The calculation is simple: subtract maintenance days from working days.

With this value in hand, simply multiply it by the number of trips per day calculated in the previous step:

Number of vehicle trips per month = operating days × number of vehicle trips per day

Important! If the result is a fractional number, do not worry. Rounding will take place only in the next step.

7. Calculate the number of vehicles needed for the operation

We have reached the final step in the fleet sizing calculation: defining the ideal number of vehicles for your operation. The process is simple — divide the number of monthly trips needed (calculated in step 3) by the number of trips each vehicle can make per month.

The formula is:

If the result is a fractional number, round up. After all, one fewer vehicle can compromise operational efficiency, and nobody wants that risk, right?

That is it! You now have the ideal number of vehicles and have completed the fleet sizing calculation accurately.

How do you calculate fleet availability?

Besides correctly sizing the fleet, it is also important to have actual fleet availability data, as these let you know how many vehicles are actually available for the operation in a given period.

Did you know low fleet availability can indicate too many vehicles in maintenance or management failures? This kind of information provides the basis for precise planning adjustments.

With that in mind, the formula to calculate fleet availability is:

Availability (%) = (Number of available vehicles / Total fleet vehicles) × 100

For example, if a fleet has 50 vehicles in total and 45 are in operation, availability will be:

(45 ÷ 50) × 100 = 90%

How do you control a fleet?

Sizing is an essential part of good fleet management, but it is not the only factor ensuring efficiency. To maintain efficient control, other practices are fundamental, including keeping track of fleet KPIs. For example, indicators such as:

• Cost per kilometer traveled;
• Fuel consumption;
• Vehicle occupancy rate.

Help identify bottlenecks and optimize fleet use.

Another important aspect is preventive maintenance. A regular maintenance plan prevents unexpected mechanical failures, increasing vehicle useful life and reducing costs.

Likewise, planning shorter, more economical routes can help reduce corrective services, besides being fundamental to optimizing fuel consumption and meeting delivery deadlines.

Finally, technology has become indispensable in fleet management. Telemetry, tracking and artificial intelligence systems allow detailed monitoring of the operation, helping managers make faster, more strategic decisions.

These are among countless other digital tools and systems available specifically for fleet management.

Now that you know how to size a fleet and maintain an efficient operation, how about taking another step to bring your management to another level?

Download our free guide to using AI in fleet management now (in Portuguese) and gain time to focus on what matters most: generating results for your company!