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MPG and Average Speed Calculator for Owner Operators

Work out your real MPG from fill-ups, your average speed with and without stops, and what driving a few mph slower could save.

1. Your MPG from fill-ups

Fill the tank to the same point each time. For each fill-up, enter the miles since the last fill-up and the gallons it took. The example rows are numbers to replace.

Fill-up 1 MPG: 6.50 mpgbest
Fill-up 2 MPG: 6.32 mpglowest

Your MPG

6.41

1,250 miles on 195 gallons

Fuel cost per mile

$0.967

at $6.20 a gallon

$/gal

The MPG adds up all the miles and all the gallons, so a big fill-up counts for more than a small one. It does not average the fill-ups' own MPG.

2. Your average speed

hrs
hrs

Speed while moving

61.1 mph

Speed with stops

50.0 mph

over 11 hours

Trip planners often use the speed with stops, because that is what gets you to the delivery on time.

3. What a different speed does to fuel

mph
mph

MPG at 65 mph

7.00

rule of thumb, not your truck

Fuel saved a year

$6,813

1,098.9 gallons

Time added per 500 miles

33 min

109.9 hours a year

Saved per hour given up

$62.00

compare with what an hour earns you

Driving 5 mph slower saves about $62.00 for every hour of driving time you give up. If an hour of your time earns you more than that, the extra speed pays. If not, slower saves you money.

The MPG at the new speed uses a rule of thumb from NACFE's driver tips, reported in FleetOwner on January 7, 2026: for every mile per hour above 60 mph, fuel economy drops by 0.1 mile per gallon. Your truck, load, trailer and terrain change this. To find your own numbers, drive the same lane at two speeds and use section 1 for each.

To price fuel for a whole trip, use the Fuel Cost Calculator. To see how far a tank goes, use the Fuel Range Planner. To turn your MPG into a full cost per mile, use the Cost Per Mile Calculator.

MPG is miles divided by gallons. Average speed is miles divided by hours, with or without the hours stopped. Your numbers stay in this browser. This is an estimate for planning.

Numbers tight? Let a dispatcher find better loads.

This tool is free. If it shows you are leaving money on the road, Grow Trucking finds loads, negotiates rates and does the paperwork for owner-operators and small fleets.

Talk to a dispatcher Call (845) 400-9179

Also: About Grow Trucking · Refer a carrier · Trucking blog

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How do you calculate MPG and average speed for a semi?

MPG is total miles divided by total gallons over several fill-ups. Average speed is miles divided by hours, and it is lower when you count the hours stopped. NACFE's rule of thumb is that each mph above 60 costs about 0.1 MPG, so a truck at 6.5 MPG at 70 mph might get about 7.0 at 65.

  1. Fill the tank to the same point each time and note the miles and gallons for each fill-up.
  2. Read your MPG and fuel cost per mile.
  3. Enter miles, hours driving and hours stopped to get your average speed.
  4. Enter your current speed and one to try, and your miles a year.
  5. Read the fuel saved and the time added, and the dollars saved for each hour given up.
  6. Test the rule of thumb on your own truck by driving one lane at two speeds.
How the numbers are worked out
NumberHow it is worked out
MPGAll miles / all gallons
Fuel cost per mileDiesel price / MPG
Speed while movingMiles / hours driving
Speed with stopsMiles / (hours driving + hours stopped)
MPG at a new speedMPG now + 0.1 x (mph above 60 now - mph above 60 at the new speed)
Dollars saved per hour given upFuel dollars saved a year / extra hours driving a year

The 0.1 MPG per mph above 60 rule is from NACFE's driver tips, reported in FleetOwner on January 7, 2026. The article also says a truck at 65 mph gets about 27 percent better fuel efficiency than one at 75 mph. The figures on fleet MPG and fuel cost are from FleetOwner's analysis of ATRI's 2026 report (2025 data): more than 7.0 MPG and $0.48 a mile. These are fleet figures and rules of thumb, not your truck's numbers.

Last reviewed September 2026. Sources: FleetOwner: NACFE's 12 driver tips for improving truck fuel economy; FleetOwner: three takeaways from ATRI's 2026 trucking cost analysis; EIA: weekly U.S. on-highway diesel prices.

Frequently Asked Questions - MPG and Average Speed Calculator

How do I calculate MPG on a semi truck?
Fill the tank to the same point each time. Then divide the miles you drove since the last fill-up by the gallons it took to fill again. For more than one fill-up, add all the miles and all the gallons, then divide. This calculator does that and shows each fill-up's own MPG so you can spot a bad one.
What is the average MPG of a semi truck?
It depends on the truck, load and route. FleetOwner's look at ATRI's 2026 report said the trucks in the study had improved to more than 7.0 MPG, and ATRI put fuel at $0.48 a mile for 2025. Owner-operators often see different numbers, so measure your own from fill-ups.
Why does my MPG change from tank to tank?
Load weight, wind, hills, speed, idling, tire pressure and how full you fill the tank all change it. One tank can be off by a lot. Use several fill-ups and add them up. The calculator flags your best and lowest fill-up so you can see the spread.
What is the average speed of a semi truck?
There are two numbers. Speed while moving is miles divided by hours driving. Speed with stops is miles divided by all the hours, including fuel, breaks and waiting. The second is lower, and it is the one to use for planning when you can arrive.
Does driving slower save fuel in a semi?
Yes, above about 60 mph. NACFE's driver tips, reported in FleetOwner on January 7, 2026, say that for every mile per hour above 60 mph, fuel economy drops by 0.1 mile per gallon. That is a rule of thumb. Your truck will differ, so drive the same lane at two speeds and compare.
How much fuel does driving 65 instead of 70 save?
Using that rule of thumb, a truck getting 6.5 MPG at 70 mph would get about 7.0 MPG at 65. Over 100,000 miles at $4 a gallon, that is about 1,099 gallons and $4,396 a year. It adds about 33 minutes to every 500 miles. The calculator shows this with your numbers.
Is it worth driving slower to save fuel?
Compare the fuel saved with the time you give up. At the example numbers (diesel at $6.20, 6.5 MPG, 100,000 miles a year), slowing from 70 to 65 saves about $62 for every hour of driving time given up. If an hour of driving earns you more than that, the extra speed pays. If not, slower saves you money.
How can I improve my semi truck's fuel mileage?
NACFE's tips include holding a steady speed, using cruise control, cutting idling, and keeping tires at the right pressure. FleetOwner's summary says a 10 percent drop in idling equals about a 1 percent gain in fuel economy. Measure your MPG before and after so you know what worked.
Does the diesel price change my MPG?
No. Price only changes what a mile costs. MPG is miles divided by gallons. The calculator uses the live U.S. average diesel price to show your fuel cost per mile, and you can enter what you actually pay.

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Go Further With MPG and Average Speed Calculator

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