Why you care: Knowing true fuel weight keeps you legal at scales, protects payload, and improves trip planning for trucks, generators, and marine tanks.
1) Two Easy Formulas
Formula A — using density (lab/supplier value)
Weight per gallon (lb/gal) = Density (kg/L) × 8.3454Example: density = 0.85 kg/L → 0.85 × 8.3454 ≈ 7.09 lb/gal.
Formula B — using API gravity (if that’s what you have)
- Compute specific gravity at 60°F:
SG₆₀ = 141.5 / (API + 131.5) - Convert to lb/gal:
lb/gal ≈ 8.34 × SG₆₀
Example: API 35 → SG₆₀ ≈ 141.5 / 166.5 ≈ 0.850 → ~7.09 lb/gal.
2) Weight by Diesel Grade (at 59°F / 15°C)
| Fuel | Typical density (kg/L) | Weight per U.S. gallon (lb/gal) | What it means |
|---|---|---|---|
| #1-D (winter/kerosene-like) | ~0.83 | ~6.93 | Lighter fuel for cold-flow; weighs slightly less per gallon |
| #2-D (on-highway ULSD) | ~0.85 | ~7.05–7.10 | Everyday road diesel; use ~7.05–7.1 lb/gal to plan |
| B20 (20% biodiesel blend) | ~0.865 | ~7.22 | A hair heavier than straight ULSD |
| B100 (neat biodiesel) | ~0.88 | ~7.34 | Heaviest of the common options |
Real fuels span roughly 0.82–0.88 kg/L → ~6.84–7.34 lb/gal.
3) Temperature Effect (Planning Table for #2 ULSD)
Colder diesel is denser (slightly heavier/gal). Warmer diesel expands (slightly lighter/gal). Use these planning values when you don’t have a density correction table handy:
| Fuel temperature (°F) | Approx. lb/gal | Note |
|---|---|---|
| 20°F | ~7.12 | Cold, winter conditions |
| 40°F | ~7.08 | Cool weather |
| 60°F | ~7.05 | Reference temp (15°C/59°F) |
| 80°F | ~6.97 | Warm ambient |
| 100°F | ~6.89 | Hot conditions |
Values are practical estimates; for custody transfer or billing, always use the supplier’s density at 15°C and official temperature-correction factors.
4) U.S. vs Imperial Gallons, Per-Liter & Per-kg
- U.S. gallon = 3.785 L. With 0.85 kg/L, that’s ~7.09 lb/gal.
- Imperial (UK) gallon = 4.546 L. Same density → ~8.52 lb/gal.
- Per liter at 0.85 kg/L: 0.85 kg ≈ 1.874 lb.
5) Gallons → Pounds Quick Table (#2 ULSD ~7.05 lb/gal)
| Gallons | Approx. pounds |
|---|---|
| 10 | ~71 lb |
| 25 | ~176 lb |
| 50 | ~353 lb |
| 75 | ~529 lb |
| 100 | ~705 lb |
| 150 | ~1,058 lb |
| 200 | ~1,410 lb |
| 300 | ~2,115 lb |
6) Worked Examples
Example A — 120 gallons of #2 ULSD
- Use 7.05 lb/gal (planning value)
- Total weight = 120 × 7.05 = ~846 lb
Example B — API data only (no density sheet)
- API = 35 → SG₆₀ = 141.5 / (35 + 131.5) ≈ 0.850
- lb/gal ≈ 8.34 × 0.850 ≈ ~7.09 lb/gal
7) Mistakes to Avoid
- Using gasoline values: Gasoline is lighter; don’t copy its numbers.
- Forgetting temperature: Hot fuel weighs a bit less per gallon than cold fuel.
- Ignoring grade/blend: #1, #2, and biodiesel blends do not weigh the same.
- Mixing units: U.S. and Imperial gallons are different sizes.
8) FAQs
How much does a gallon of diesel weigh?
Plan on ~7.0–7.1 lb/gal for #2 ULSD at 59°F (15°C). Real-world diesel across grades and temperatures ranges ~6.84–7.34 lb/gal.
Which weighs more per gallon: #1 or #2 diesel?
#2 diesel is denser and typically weighs a bit more per gallon than #1 diesel.
Do biodiesel blends change weight?
Yes. Blends like B20 nudge weight upward vs. straight ULSD; neat biodiesel (B100) is heavier still.
How do I convert liters of diesel to pounds?
Multiply liters by the density (kg/L), then by 2.20462 to get pounds. At 0.85 kg/L, 1 L ≈ 1.874 lb.
What number should I use near a scale house?
For a conservative buffer on #2 ULSD, plan with 7.1–7.2 lb/gal if you’re close to limits.