A US gallon of diesel weighs approximately 7.1 pounds at 60°F, with a typical range of about 6.9 to 7.3 pounds per gallon depending on temperature and fuel blend. That means a full set of 100–300 gallon truck tanks adds roughly 700 to 2,100 pounds to your gross vehicle weight.
For comparison, water weighs 8.34 pounds per gallon — diesel is lighter and floats on water — and gasoline is lighter still at roughly 6.1–6.3 pounds per gallon.
Here's the quick math, why it matters at the scale house, and how temperature moves the number.
How Much Does a Gallon of Diesel Weigh?
The commonly cited standard is about 7.1 pounds per US gallon at 60°F (roughly 0.85 kg per liter), which is the reference temperature the fuel industry uses for measurement. In everyday terms, truckers round it to "about 7 pounds a gallon" — close enough for scale-house math.
The exact figure shifts slightly because diesel is not one fixed formula:
- #2 diesel (standard on-highway fuel) sits near the 7.1 lb/gal mark.
- #1 diesel and winter blends are slightly lighter, since #1 is a thinner cut closer to kerosene.
- Biodiesel blends run marginally heavier than straight petroleum diesel.
- Temperature moves density up or down — more on that below.
For trip planning and weight estimates, 7 lb per gallon is the safe working number.
Diesel Weight Quick Reference Table
Approximate weights using 7.1 lb per US gallon:
| Gallons of diesel | Approximate weight |
|---|---|
| 1 | 7.1 lb |
| 20 | 142 lb |
| 50 | 355 lb |
| 100 | 710 lb |
| 120 | 852 lb |
| 150 | 1,065 lb |
| 200 | 1,420 lb |
| 250 | 1,775 lb |
| 300 | 2,130 lb |
Why Diesel Weight Matters for Truckers
Fuel weight isn't trivia — it's part of your legal payload math.
Gross and axle weight limits. The federal interstate limit is 80,000 lb gross, with 12,000 lb typically allowed on the steer axle and 34,000 lb on each tandem. If you scale out heavy, the 1,400+ pounds sitting in a pair of full 100-gallon tanks is often the difference. Fueling after you scale a heavy load — or taking on half tanks — is a standard move for a reason.
Bridge formula and axle distribution. Fuel tanks hang near the steer and drive axles, so a full fill shifts weight onto the axles that are usually closest to their limits. Many drivers hauling max-weight loads plan fuel stops to keep steer and drive axles legal, not just the gross.
Fuel planning and cost per mile. At roughly 7 lb per gallon, every 1,000 lb of fuel you carry is about 140 gallons. Carrying extra fuel weight costs a small amount of efficiency; running tanks too low costs flexibility to buy where fuel is cheap. The bigger lever, though, is price per gallon — a fuel card like the CFX Fuel Savings Program saves carriers an average of 45¢ per gallon at 5,000+ locations, which matters far more to your bottom line than any weight tweak. To see what fuel really does to your numbers, run your cost per mile.
Does Temperature Change How Much Diesel Weighs?
Yes, slightly. Diesel expands as it warms and contracts as it cools, so a gallon of hot fuel weighs a bit less than a gallon of cold fuel. The swing between a cold winter fill and a hot summer fill is on the order of a few tenths of a pound per gallon — a couple percent of density across a wide temperature range.
Practical takeaways:
- Across full tanks, the summer-vs-winter difference amounts to roughly tens of pounds, not hundreds — rarely enough to change a scale ticket outcome on its own.
- You buy fuel by volume, so in theory cold, denser fuel gives you marginally more energy per gallon. In practice, retail pumps don't adjust for temperature, and the effect is too small to chase.
- Winter-blended diesel (with #1 or additives) is slightly lighter per gallon than straight summer #2.
FAQ: Diesel Weight
How much does a full tank of diesel add to truck weight?
A typical semi carries two tanks of 100–150 gallons each. At about 7.1 lb per gallon, that's roughly 1,420 lb for two 100-gallon tanks and about 2,130 lb for 300 total gallons. Rule of thumb: figure about 700 lb per 100 gallons.
Does diesel weigh more than gasoline?
Yes. Diesel is about 7.1 lb per gallon versus roughly 6.1–6.3 lb for gasoline — diesel is a denser fuel, which is also part of why it carries more energy per gallon.
Does diesel weigh more than kerosene?
Slightly. Kerosene and #1 diesel are close cousins at roughly 6.8 lb per gallon, a bit lighter than standard #2 diesel. That's why winter blends, which cut #2 with #1, weigh marginally less.
Does burning fuel change my axle weights during a trip?
Yes — as you burn fuel, weight comes off the axles nearest your tanks (mostly steer and drives). If you scale barely-legal on the drives with full tanks, you'll get lighter as you run. The reverse matters more: don't scale legal on fumes and then add 1,000+ lb of fuel before the next open scale.