Gallons · Pounds · SG

Gallons to pounds calculator for any liquid

Know what the drum weighs before the invoice tells you.

Last updated 2026-09-27. Math runs in your browser, no data leaves your computer.

Type a quantity in any of the four units and the specific gravity from the SDS. The tool converts both ways, so it works for sizing an order in gallons and for checking a weight ticket in pounds.

Use the number on the purchase order or the tank gauge, before any rounding to full drums or totes.

The gallon here is the 231 cubic inch gallon, 3.785411784 liters by definition in NIST Handbook 44.

Take the value from SDS Section 9 or the certificate of analysis for your lot. Water is 1.00, most solvents sit below it, and strong acid or caustic solutions sit well above.

Before the booking, screen the name on the invoice. Shipment pre-check is on the paid plans, from USD 59 a month.

General guidance only. Verify against the cited primary sources before you commit to a shipment, declaration, or contract.

How gallons turn into pounds

Chemicals are priced by weight and handled by volume, and specific gravity is the only bridge between the two. The unit definitions fix everything else: NIST Handbook 44 Appendix C defines the US gallon as 231 cubic inches, or 3.785411784 liters, and the avoirdupois pound as exactly 0.45359237 kilograms.

A liquid at 1.000 g/mL therefore weighs 3.785411784 / 0.45359237 = 8.3454 lb per gallon, which is the same 119.8264 kg/m³ per lb/gal factor that NIST SP 811 Appendix B lists. Multiply that by the SG and you have the weight of one gallon of your product. In metric the step is simpler still, because a liter of a liquid with SG 1.25 weighs 1.25 kg.

The 8.34 lb per gallon figure people carry around in their heads is water. USGS gives water at 60 °F as 0.99907 g/cm³, which works out to 8.338 lb per gallon, and it is the right number only when you are buying something that behaves like water.

SG on an SDS is usually quoted against water at a stated temperature, often 20 °C or 60/60 °F. Water weighs 0.99823 g/mL at 20 °C in NBS Circular 440 and 0.99907 g/cm³ at 60 °F in the USGS table, so an SG on either basis sits within 0.2 percent of the true density in g/mL. That gap is inside the rounding of most SDS values, and the tool treats the two as the same number.

Worked example: 4,000 gallons of caustic soda 50%

The booking. You need 4,000 gallons of caustic soda 50% and the supplier prices it per pound delivered. You multiply by 8.34 lb per gallon because that is the number everyone remembers, get 33,360 lb, and build the budget and the freight booking on it, which looks fine on paper.

The failure. The 8.34 figure is water, and the caustic is far heavier. At the SG of 1.5253 the Sourzi density calculator carries for this grade, one gallon weighs 1.5253 × 8.3454 = 12.73 lb, so 4,000 gallons weigh 50,917 lb and the invoice lands 53 percent above budget. The choice is the usual one: cut the gallons, or raise the budget.

The fix. Run the SG from Section 9 of the supplier's SDS before the order goes out. Holding the 33,360 lb budget, the tool returns 33,360 / 12.73 = 2,621 gallons, and the freight booking now carries the real weight, so the load ships at the price you planned.

Buying by the ton instead of the gallon? The tons to gallons calculator handles short, metric, and long tons at /tools/chemicals/tons-to-gallons-calculator.

If the SDS gives density in lb/gal, kg/m³, Baumé, or API gravity rather than SG, the specific gravity converter turns any of them into the number this tool needs at /tools/chemicals/specific-gravity-converter.

Frequently asked

How many pounds are in a gallon?

A US gallon of liquid weighs its specific gravity times 8.3454 pounds. That factor comes straight from the unit definitions in NIST Handbook 44: a gallon is 3.785411784 liters and a pound is 0.45359237 kilograms, so one gallon of a liquid at 1.000 g/mL weighs 3.785411784 / 0.45359237 = 8.3454 lb. A liquid at SG 1.25 weighs 1.25 × 8.3454 = 10.43 lb per gallon.

Why not just use 8.34 pounds per gallon?

Because 8.34 is water, and almost nothing you buy by the drum is water. USGS lists water at 60 °F at 0.99907 g/cm³, which is 8.338 lb per gallon. A liquid with SG 1.5 weighs half as much again per gallon, so a budget built on the water number comes in 50 percent light.

Where do I find the specific gravity of my chemical?

Section 9 of the Safety Data Sheet, under physical and chemical properties, usually listed as relative density or specific gravity with a temperature. The supplier's certificate of analysis for your actual lot is better still, because concentration moves the number. For a 50 percent solution, a few points of strength shift the SG in the second decimal.

Does temperature change the answer?

Yes, slightly, because liquids expand as they warm and a gallon weighs less at 100 °F than at 60 °F. If the SDS quotes SG at 60/60 °F against water at 60 °F, the true lb per gallon is about 0.1 percent below what this tool shows, which sits inside the rounding of most SDS values. For larger swings, run the density at temperature calculator first.

Need a factory for this chemical?

Tell us the chemical, grade and quantity. A person on our team in Shanghai sends you a real, checked factory, and your first one is free.

Get your free Factory Match Or talk to our team

Related tools

Sourzi shows what official files say. It is not customs or legal advice. For a binding answer, ask a licensed customs broker, a CBP ruling or an Australian Border Force Tariff Advice.

File dates and links are on Data sources.