Fuel Consumption Calculator — Diesel & Gas (GPH / MPG)
Use this calculator to estimate how much fuel your trucks, generators, heavy equipment, or
marine vessels burn per day, month, and year. Pick an equipment type to start with an
industry-standard consumption rate, then enter your own mileage or run-hours for a more
precise gallons-per-day, gallons-per-month, and gallons-per-year estimate — plus an
estimated fuel spend if you enter your price per gallon.
Fuel Consumption Formulas
Fuel consumption is calculated two ways depending on the type of equipment:
- Road vehicles (miles-based): gallons = miles driven ÷ MPG. Multiply by
number of vehicles and operating days per month for fleet totals.
- Stationary and marine equipment (hours-based): gallons = hours run × GPH
(gallons per hour). Multiply by number of units and operating days per month for total
volume.
Typical Fuel Consumption by Equipment Type
| Equipment | Typical Consumption |
| Semi truck (long-haul, heavy-duty) | ~6.5 MPG diesel |
| Box truck / medium-duty | ~9 MPG diesel |
| Pickup truck / cargo van | ~15 MPG gasoline or diesel |
| 20 kW diesel generator | ~1.6 GPH at 75% load |
| 50 kW diesel generator | ~2.9 GPH at 75% load |
| 100 kW diesel generator | ~5.0 GPH at 75% load |
| 250 kW diesel generator | ~12.9 GPH at 75% load |
| 500 kW diesel generator | ~26.4 GPH at 75% load |
| Heavy equipment / excavator | 3-8 GPH (avg ~5 GPH) |
| Marine vessel | Varies by engine — use manufacturer-rated GPH |
See the full diesel generator fuel consumption chart
(GPH at 75% load, with 24-hour gallon equivalents by generator size) below.
How to Estimate Consumption by Fleet Type
For a truck fleet, start with your telematics or fuel-card monthly mileage per vehicle and
your fleet's average MPG (heavy-duty trucks run 6-7 MPG loaded, medium-duty box trucks run
8-10 MPG, and light-duty pickups or vans run 13-17 MPG). For generators, match your unit's
rated kW to the closest row in the table above, or use the GPH figure from your generator's
spec sheet at your typical load percentage — fuel burn scales roughly with load, so a
generator running at 50% load burns meaningfully less than the 75%-load figures shown here.
For heavy equipment such as excavators, loaders, and bulldozers, 3 to 8 GPH is a reasonable
planning range depending on machine size and duty cycle; refer to the OEM's fuel consumption
chart for your specific model when precision matters. For marine vessels, GPH varies widely
by engine displacement, hull type, and cruising speed — use your engine manufacturer's rated
GPH at your typical RPM, since there is no single industry-standard figure that fits all
vessel types.
When Bulk Fuel Delivery Makes Sense
Once you know your monthly gallon volume, the next question is how to source that fuel most
efficiently. Operations consuming roughly 500 gallons per month or more — a mid-sized
generator running daily, a handful of heavy-duty trucks, a small excavation fleet, or a
cluster of backup generators across a property — are typically strong candidates for on-site
bulk fuel delivery instead of retail pump
fueling or manual jerry-can refueling. Bulk delivery brings the fuel to your trucks,
generators, or job site on a scheduled or on-demand basis, which cuts driver downtime,
avoids running dry during a job or an outage, and often unlocks wholesale-based pricing at
higher volumes. If you already know roughly how much you spend and want to see the dollar
comparison against retail pricing, use our
Fuel Cost Savings Calculator. To get a delivered-fuel
quote sized to the volume you just calculated, request a quote below or call Exigo Fuels at
(305) 900-6725 — or start at our
quote page for a full request form.
Frequently Asked Questions
How do you calculate fuel consumption?
For vehicles that travel a distance, fuel consumption in gallons equals miles driven divided
by miles per gallon (gal = miles ÷ MPG). For equipment that runs on a time basis —
generators, heavy equipment, and marine engines — fuel consumption equals hours run
multiplied by the engine's gallons-per-hour rating (gal = hours × GPH). Multiply by
the number of units and operating days to get monthly and annual totals.
How many gallons per hour does a diesel generator use?
At roughly 75% load, a 20 kW diesel generator burns about 1.6 GPH, a 50 kW unit about 2.9
GPH, a 100 kW unit about 5.0 GPH, a 250 kW unit about 12.9 GPH, and a 500 kW unit about 26.4
GPH. Actual consumption varies with load factor, ambient temperature, and generator
efficiency — lightly loaded generators burn noticeably less per hour, while generators run
near 100% load burn more.
How much fuel does a semi truck use per mile?
A loaded semi truck averages around 6 to 6.5 miles per gallon, meaning it burns roughly 0.15
to 0.17 gallons of diesel per mile. Box trucks and medium-duty trucks typically get 8 to 10
MPG (about 0.10 to 0.13 gal/mile), while pickup trucks and cargo vans average 13 to 17 MPG
depending on load and terrain.
How do I convert MPG to gallons per month?
Divide your monthly miles by your vehicle's MPG to get monthly gallons (gallons = monthly
miles ÷ MPG). For a fleet, multiply that per-vehicle figure by the number of
vehicles. The calculator on this page does this automatically — enter miles per day, MPG,
number of vehicles, and operating days per month to see your monthly and annual gallon
totals.
What's the difference between this and the fuel cost calculator?
This calculator estimates how much fuel you consume — gallons per day, month, and year —
based on your mileage or run-hours. Our separate
Fuel Cost Savings Calculator estimates how much money
you could save by switching from retail pump fueling to on-site bulk delivery, for fleets
that already know their consumption. Use this tool first to find your volume, then the
savings calculator to see the cost comparison.
What factors affect real-world fuel consumption?
Load factor, terrain, idle time, ambient temperature, engine age and maintenance, and duty
cycle all affect real-world fuel burn. A generator running at 50% load burns meaningfully
less per hour than one at 100% load; a truck climbing grades or idling in traffic burns more
per mile than highway cruising. Treat calculator estimates as a planning baseline and adjust
using your own fuel logs when available.
