How Much Do a Gallon of Diesel Fuel Weigh — and What You Need Alongside That Number

A gallon of No. 2 diesel weighs about 7.1 pounds — 3.22 kilograms — at 60°F, the reference temperature the petroleum industry uses for volume and density. That gives you 178 pounds for 25 gallons, 710 pounds for 100 gallons, and 1,420 pounds for 200 gallons. Real deliveries run 6.9 to 7.2 pounds per gallon depending on grade and source. B100 biodiesel is heavier at roughly 7.33 pounds per gallon, and an Imperial gallon is 1.201 US gallons, so it comes to about 8.53 pounds.

The figure is the easy part

Six things sit between 7.1 lb/gal and a number you can defend at a scale house. Ranked by how far each one moves a 100-gallon load:

1. How many gallons are actually in there. Rated capacity is a product name. Nobody measured your tank. Fill necks, baffles, expansion space, and a sender that reads full across the top third of its travel put an eight-gallon gap between "topped off" and 100 without anyone lying to you. That gap is 57 pounds.
2. The tank itself. Better Built lists its 100-gallon aluminum L-shaped transfer tank at a 134-pound ship weight. Greer's spec table for a 1,000-gallon UL-142 double-wall cylindrical tank gives 1,478 pounds bare and 2,154 pounds on a skid. People run the fuel math and then forget the steel entirely.
3. Grade and batch. That 6.9-to-7.2 spread is 30 pounds across 100 gallons, and nothing on the pump tells you where in the range your delivery landed.
4. Temperature. Diesel near 850 kg/m³ expands about 0.00046 per °F, so filling the same tank at 95°F instead of 40°F puts roughly 18 fewer pounds in it.
5. Blend. B20 against straight No. 2 is a five-pound difference on 100 gallons.
6. Meter error. NIST Handbook 44 allows a maintenance tolerance of ±0.5 percent on a retail dispenser, which is 3.5 pounds on that same load.

The bottom three are noise. The top two are what actually gets a trailer over its rating, and the second one is the one I see missed most.

Weight by grade, blend, and gallon basis

The US gallon is 231 cubic inches exactly, or 3.7854 liters. The Imperial gallon is 4.54609 liters. If a spec sheet, a marine manual, or a Canadian supplier is quoting Imperial and you multiply by 7.1, you are nearly 17 percent light before you start.

| Fuel | lb / US gal at 60°F | kg / US gal | lb / Imperial gal | 100 US gal | |---|---|---|---|---| | No. 1-D (winter grade) | 6.92 | 3.14 | 8.31 | 692 lb | | No. 2-D ULSD | 7.10 | 3.22 | 8.53 | 710 lb | | B5 | 7.11 | 3.23 | 8.54 | 711 lb | | B20 | 7.15 | 3.24 | 8.59 | 715 lb | | B100 | 7.33 | 3.32 | 8.80 | 733 lb |

The B5, B20, and B100 lines are volumetric blends of the No. 2 and B100 figures, which is how blenders build the product and close enough for load planning. Winter No. 1-D matters more than most people expect: a full 200-gallon auxiliary tank swaps 36 pounds between January and July purely on grade.

Four records to read before you multiply

Diesel grade comes off the bill of lading or the supplier's certificate of analysis, not the pump. ASTM D975 covers seven grades — No. 1-D, No. 2-D, and No. 4-D at three sulfur levels — and it is worth knowing that D975 sets no density limit at all. Cetane, flash point, cloud point, viscosity, sulfur, water and sediment: those are specified. Density is measured separately, usually by ASTM D4052, and reported on the certificate.

Blend percentage is on the dispenser by law. Under 16 CFR Part 306, blends above 5 percent and up to 20 percent carry a "B20 Biodiesel Blend" label, so anything between B6 and B20 announces itself. B5 and below need no label, which is exactly why B5 sits in the table above — you may be buying it without knowing.

Gallon basis is US unless something tells you otherwise. Check any document that crossed a border.

Fuel temperature is the one you have to observe yourself. US retail dispensers sell gross gallons at whatever temperature the fuel comes out of the ground; NIST Handbook 44 permits automatic temperature compensation but does not require it, and American retail has not adopted it the way Canada has. Underground tanks in July run warmer than the air. A fresh delivery into a hot aboveground tank runs warmer still.

Which volume number to trust

For a rough load calculation, use the pump ticket, not the gauge. A dispenser tested to Handbook 44 must deliver between 4.975 and 5.025 gallons on a five-gallon prover test — ±0.5 percent in service, ±0.3 percent when newly installed or adjusted. Nothing on your equipment comes close to that. A float sender in a baffled tank on a sloped shoulder is a mood, not a measurement.

Three usable volume records, best first:

A metered fill ticket from a dispenser under state weights-and-measures inspection. A supplier's delivery ticket with gallons and net-versus-gross basis stated. Your own dipstick reading against a strapped tank chart, if the tank came with one.

Where this gets slippery: a metered ticket tells you what went in, not what is in there now. Add the ticket to a starting volume you can defend, or run the tank down to a known point first. I have watched an owner add 60 metered gallons to a tank he assumed was near empty, when it held 45. That is 745 pounds when he had planned for 425.

Petroleum diesel against a biodiesel blend

Both get quoted as near-fixed weights, and for load planning both essentially are. B100 is about 3.2 percent heavier than No. 2 — 7.33 against 7.10 — because methyl esters are denser than the hydrocarbon cut they replace. Diluted to B20 under ASTM D7467, that becomes a 0.7 percent difference. On 100 gallons, five pounds.

Put that beside the ordinary batch-to-batch spread of straight No. 2 diesel, 6.9 to 7.2 lb/gal, and the blend correction is roughly one sixth the size of the variation you already tolerate without thinking about it. Chasing the blend number while guessing at gallons is backwards.

Where the blend genuinely changes your calculation is in the paperwork it enables. B6-to-B20 fuel is sold against D7467, whose biodiesel component must meet D6751, and suppliers of blended product routinely issue a certificate showing measured density. Straight rack diesel often arrives with nothing. If you need a real density figure rather than a table value, blended fuel is frequently the easier place to get one.

The assumptions that turn the estimate unsafe

Water and sediment

D975 and D7467 both cap water and sediment at 0.05 percent by volume. That is a fuel-quality limit. Weight-wise, 0.05 percent of 100 gallons is a twentieth of a gallon. Water in a tank does not meaningfully change what you weigh. It changes whether you make the trip.

Temperature, correctly scoped

The 0.00046 per °F coefficient describes volume, and mass does not care about temperature. Cold fuel means more pounds in a fixed tank; warm fuel means fewer. Across a 55-degree swing that is about 18 pounds on 100 gallons — real, but smaller than one passenger. ASTM D1250, the joint API MPMS Chapter 11.1 procedure, derives the coefficient from measured density rather than assuming a flat value, and it exists for custody transfer, where a percent of a barge load is money. For deciding whether your trailer is legal, temperature is the last correction you should reach for.

The ratings that actually bind

Payload is GVWR minus the vehicle as it sits, and "as it sits" includes the bed liner, the toolbox, the tongue jack, and the fuel already in the factory tank. GAWR is per axle and is stamped on the certification label; on a multi-axle trailer each axle must be listed separately even when the ratings are identical.

Tires are the piece I get called about. Under FMVSS No. 120 — No. 110 covers trailers rated at or below 10,000 pounds — the sum of the maximum load ratings of the tires on an axle must be at least the GAWR for that axle — a floor, not a target. RVIA guidance asks for a 10 percent reserve above certified GAWR, and manufacturers frequently do not build one in. An ST225/75R15 in Load Range D carries 2,540 pounds at 65 psi; the same size in Load Range E carries 2,830 pounds, but only at 80 psi. Run that E tire at 65 psi and you are back to 2,540, which is why a load range upgrade without a pressure change buys nothing.

Thunder rolled once about twenty minutes ago and quit, and the air has not cooled, which is the whole problem with checking pressure at a fuel stop. Cold inflation pressure means measured before the trailer moves, at ambient. Adding 700 pounds of fuel to a trailer whose tires you last set warm, three months ago, is how the call to me starts.

The question nobody asks: where the fuel sits

Total weight is only half of it. Seven hundred pounds ahead of the trailer axles becomes tongue weight; the same 700 pounds behind them lifts the tongue and starts sway. The usual target is 10 to 15 percent of gross trailer weight on the tongue, and a transfer tank mounted at the front of a pickup bed pushes that number the other way by loading the truck's rear axle.

Side to side is where I earn my living. Trailer axles almost never load evenly, and a scale gives you axle totals, not corners. So when I get to a shoulder, I read the tire that did not fail before I touch the jack — its wear pattern, its date code, its remaining pressure. The survivor carries the setup evidence. A failed carcass tells you it failed. The one across from it tells you what the load and the pressure were doing for the last eleven hundred miles. I can document that. I am not going to rate a damaged axle from a photograph.

Near your rating with a full tank? Weigh it

If the arithmetic puts you within a few hundred pounds of any rating, the arithmetic is finished doing useful work. Weigh the rig.

1. Load the trailer exactly as you will travel — gear, water, batteries, the boat or bikes strapped down — and fill every fuel tank. Departure with a full tank is your worst case.
2. Drive onto a CAT Scale with the steer axle on platform 1, drive axle on platform 2, and the trailer axles on platform 3. Spread-axle trailers use the app's spread-axle option and a second position.
3. Read each axle against its GAWR, then the total against GVWR and GCWR. Being under gross while over the truck's rear axle rating is the common result, because tongue weight lands there.
4. Pull off the scale, disconnect in the lot — never on the platform — drop the weight-distribution bars, and reweigh the truck alone. Rear axle loaded minus rear axle solo is your tongue weight.
5. Compare each axle total against the sum of its tires' sidewall ratings at the cold pressure you are actually running, not the pressure on the placard.

CAT guarantees axle weights as well as gross, and will send a representative to court if a state scale contradicts a legal ticket. Roughly $15 for the first weigh, about $5 for a qualifying reweigh on the same scale within 24 hours. A reweigh after you shift cargo is the cheapest engineering you will buy.

When a rule of thumb is no longer enough

Use a supplier certificate when the fuel is inventory rather than a fill-up: bulk deliveries, generator tanks, anything where a density figure carries into a bill. Ask for measured density at 15°C by D4052 and the net-versus-gross basis of the invoice.

Use a calibrated meter or a strapped tank chart when the same tank gets drawn down and refilled repeatedly and you need running totals rather than a single snapshot.

Use a public scale whenever a calculated total lands within about 5 percent of a rating, whenever the configuration changes — different boat, different tow vehicle, added tank — and once a season regardless. Estimates drift. Scales do not.

Tracking it across a season

One page per rig, updated at each fill: date, gallons metered, grade and blend from the pump, ambient temperature, and the tank's reading before and after. Add the scale ticket whenever you buy one, and the DOT date code from each tire when it goes on.

The calculator cannot tell you what your gallons weighed on the day the right-side tire came apart. That log can. Three fills of pattern beats any table value, including the ones above.

FAQ

How much do 200 gallons of diesel weigh in pounds?

About 1,420 pounds of No. 2 diesel at 7.1 pounds per gallon, 60°F. Expect 1,380 to 1,440 pounds across the normal 6.9-to-7.2 range, or about 1,430 pounds for a B20 blend. Then add the container — two of the 100-gallon aluminum transfer tanks cited above are another 268 pounds.

How many gallons of diesel weigh 100 pounds?

Just over 14 gallons — 100 divided by 7.1 is 14.1 US gallons of No. 2 diesel at 60°F. Batch density shifts that between 13.9 and 14.5 gallons. In metric terms, 100 pounds is 45.4 kilograms, which is about 53.3 liters of diesel at 0.851 kg/L.

How many gallons of diesel equal 2,000 pounds?

About 282 US gallons at 7.1 pounds per gallon. The realistic band runs 278 to 290 gallons depending on grade and temperature, and a B20 blend reaches 2,000 pounds at roughly 280 gallons. One short ton of diesel therefore occupies a little more than a quarter of a 1,000-gallon tank.

How much does a 1,000-gallon diesel tank weigh?

Empty, Greer's UL-142 double-wall cylindrical tank is 1,478 pounds bare, 1,679 pounds on a cradle, 2,154 pounds on a skid. Full of diesel adds 7,100 pounds. Plan foundations and lifting for roughly 8,600 to 9,300 pounds gross, depending on the mounting.

How much does a gallon of diesel weigh in kilograms?

About 3.22 kilograms per US gallon of No. 2 diesel at 60°F, from a density near 0.851 kg/L. B100 biodiesel runs about 3.32 kilograms per US gallon. An Imperial gallon, being 4.54609 liters against the US gallon's 3.7854, weighs about 3.87 kilograms of the same fuel.

How much does 25 gallons of diesel weigh?

Roughly 178 pounds, or 80.5 kilograms, for 25 US gallons of No. 2 diesel at 60°F. The realistic range is 173 to 180 pounds. A B20 blend comes to about 179 pounds. That is close enough to two adult passengers to matter on a light trailer near its axle rating.

How does fuel temperature change density?

Diesel expands roughly 0.00046 per °F, so warm fuel is less dense and a gallon of it weighs slightly less. Filling a fixed tank at 95°F instead of 40°F puts about 2.5 percent less mass in it. ASTM D1250 derives the exact coefficient from measured density rather than assuming one.