Ask ten fleet owners what a kilometre costs them and you’ll get ten confident answers. Most are based on diesel alone, which is the biggest cost but never the whole story. Add everything up properly, and the number is usually higher than people expect. A fuel monitoring system takes care of the biggest piece of that puzzle. The rest is arithmetic and a bit of discipline.
This post covers both: how to calculate fleet cost per km, and how to figure out which part of it is leaking.
What “cost per km” actually means
Total cost of running a vehicle for a period, divided by the kilometres it ran in that period. That’s the whole formula.
Cost per km = total cost ÷ total km
Two things trip people up straight away.
First, which kilometres? Use all of them, loaded and empty. Empty return trips cost money too, and ignoring them makes the number look better than the truck’s real life. You can track loaded km separately if you like, but don’t use it as your main figure.
Second, which period? A month works well. A single trip is too noisy, and a full year hides problems for too long.
What goes into the total
Think of two buckets.
Running costs rise and fall with the kilometres: diesel, tyres, maintenance and repairs, tolls, and trip allowances.
Fixed costs arrive whether the truck moves or not: EMI, insurance, permits and taxes, parking, and usually the driver’s base salary.
Where you put the driver is a judgement call. Some owners treat salary as fixed, others split it. Pick one way and stay with it, otherwise your month-to-month numbers won’t compare.
A worked example
These numbers are made up to show the maths, so swap in your own. One truck, one month, 6,000 km.
| Cost | Per month | Per km |
| Diesel (1,800 litres at ₹90) | ₹1,62,000 | ₹27.00 |
| Driver and helper | ₹32,000 | ₹5.33 |
| Tyres (monthly share) | ₹10,000 | ₹1.67 |
| Maintenance and repairs | ₹12,000 | ₹2.00 |
| Tolls | ₹18,000 | ₹3.00 |
| EMI | ₹55,000 | ₹9.17 |
| Insurance (monthly share) | ₹6,000 | ₹1.00 |
| Permits and other fixed | ₹3,000 | ₹0.50 |
| Total | ₹2,98,000 | ₹49.67 |
So this truck costs about ₹50 for every kilometre it runs. Notice that diesel alone is over half of it.
Now run the same truck for 4,500 km instead, because it sat idle for a week. The EMI, insurance, permits and driver’s salary don’t shrink, about ₹96,000 in all. The running costs scale down with the kilometres. The total comes to roughly ₹2,47,500, and the cost per km jumps to about ₹55.
Same truck, same driver, same diesel price. A quarter fewer kilometres added more than ₹5 to every kilometre. That’s why cost per km is as much a utilisation number as a spending number.
Where the money leaks
Once you have your number, the real question is which line is bloated. Here’s where I’d look, roughly in this order.
Fuel
I’d start here because it’s the biggest, not because it’s the most interesting. Fuel leaks in three ways: engines idling for long stretches, routes longer than they need to be, and fuel that never reaches the engine at all.
Small changes matter more than they look. If our example truck’s mileage slips from 3.3 to 3.0 km per litre, it burns about 200 extra litres a month. That’s an extra ₹18,000, or ₹3 on every kilometre, from a mileage change most drivers wouldn’t even notice.
Telling theft from plain waste is worth its own read, and we’ve covered the warning signs of fuel theft separately.
Dead kilometres and idle days
Empty returns, trucks waiting for a load, vehicles parked for days. None of it shows up as an expense, but all of it pushes cost per km up, as the example showed. If you want a closer look at the problem, our post on improving fleet vehicle utilisation goes into it. A vehicle tracking system shows trips, stoppages and idle time per vehicle, so you can see how many days each truck really worked.
Tyres
They’re a quiet cost: pressure slips, a tyre wears unevenly, and then it’s a replacement at the wrong time. If tyres look expensive on your sheet, our guide on how tyre monitoring lowers tyre cost per km goes deeper.
Breakdowns and late servicing
A breakdown costs you the repair, the tow, the missed delivery and the days the truck is off the road. Most of that is avoidable with servicing on time, and maintenance reminders are a plain, boring fix that works.
Driving habits
Harsh braking, hard acceleration and speeding burn more fuel and wear out brakes and tyres faster. It shows up across several lines at once, which is why it’s easy to miss. Driver behaviour monitoring gives you speed, braking and idling patterns per driver, and coaching tends to work better than blame.
Waiting at loading points
Two hours of detention per trip doesn’t look like much until you multiply it by every trip in a month. Idle time reports show where trucks wait, and sometimes the fix is a conversation with the customer, not the driver.
Getting the numbers without drowning in spreadsheets
The weak spot in most cost per km sheets is the data, not the formula. Diesel litres come from slips someone wrote by hand. Kilometres come from an odometer reading noted late. Everything is approximate, and the result looks precise.
A better way is to take what you can from systems that measure automatically:
- Kilometres: from GPS trip data, not from memory
- Fuel: from tank sensors, not from slips
- Idle and stoppage time: from tracking reports
- Everything else: (EMI, insurance, permits, salaries) from your accounts, once a month
Sahaj’s fuel reports include things like fuel trip cost, fuel economy and tripwise consumption, plus a fuel expense summary. Its vehicle tracking also includes expense management to record vehicle-related costs. You’d still add the fixed costs yourself. No system knows your EMI.
A routine that takes about an hour a month
- Collect last month’s costs by vehicle.
- Pull the km run for each vehicle from trip data.
- Work out cost per km, and split it into the lines from the table above.
- Compare vehicles on similar routes, and look at the one that stands out.
That’s it. The hardest part isn’t the calculation, it’s doing it every month.
Mistakes that make the number useless
- Using only loaded kilometres
- Leaving out fixed costs because “they’re paid anyway”
- Mixing monthly and yearly figures
- Counting the driver one way one month and another way the next
- Comparing a truck on a long highway route with one in city traffic, as if they’re the same thing
- Working it out once and never looking again
How SAHAJ GPS helps
SAHAJ GPS Fuel Monitoring System combines GPS tracking with fuel sensors in the tank. For cost per km work, the parts that matter most are:
- Real-time fuel level monitoring
- Fill and drain alerts, with the amount and the time
- Consumption reports, fuel trip cost and fuel economy reports
- Fuel expense summary
- Support for multiple sensors on large or dual tanks
One practical point: it needs a compatible GPS tracker and good fuel sensors on the vehicle. It’s not software alone. The vehicle tracking system adds trip history, stoppage and idle reports, driver behaviour data and expense records, which cover most of the other pieces.
Frequently asked questions
How do I calculate fleet cost per km?
Add up everything you spent on a vehicle in a month, including fuel, driver, tyres, maintenance, tolls, EMI and insurance, then divide by the kilometres it ran.
Should I include empty kilometres?
Yes. Empty runs cost money, so leaving them out makes your number look better than reality. You can track loaded km as a second figure.
What’s the biggest part of cost per km?
For most trucks it’s fuel, though the exact share depends on your vehicle, routes and diesel price.
Why does cost per km go up when a truck sits idle?
Fixed costs like EMI, insurance and base salary stay the same, so they’re spread over fewer kilometres.
Can GPS tracking help lower cost per km?
It doesn’t lower it by itself, but it shows where kilometres, fuel and idle time go, which is where most of the leaks are.
One more thing
Don’t wait for a perfect sheet. A rough cost per km worked out this month beats a perfect one you never build. And if you’d like to see what fuel and trip data look like for your own vehicles, talk to the SAHAJ GPS team for a demo.