100 cubic feet to gallons

One hundred cubic feet is 748.051948 US gallons

The 231 cubic inch check, and the metric side

One hundred cubic feet is 748.051948 US gallons, and the multiplication is the ratio itself: 100 x 7.48051948051948 = 748.051948. A second route through cubic inches lands on the same number. One hundred cubic feet is 100 x 1,728 = 172,800 cubic inches, and 172,800 / 231 = 748.051948, because a US gallon is 231 cubic inches.

The metric side comes from the inch as well. One hundred cubic feet is 100 x 28.316846592 = 2,831.6847 liters, and 2,831.6847 / 4.54609 = 622.8835 imperial gallons. The NIST Guide to the SI, Appendix B lists both gallon definitions on one page, which is how a US price and a UK price get compared without guessing at the difference.

The number a delivery ticket uses is the cubic yard, because soil, mulch, sand and gravel are sold that way. A yard is 27 cubic feet, so 100 / 27 = 3.7037 cubic yards. Print the two together and the ticket stops looking like a mystery: 3.7037 yards and 748.051948 gallons describe the same pile.

Every section below starts from that one figure. A drum count, a bag count, a freight bill and a gas reading are four ways of asking what 748 gallons looks like in practice.

748 gallons in the drums, totes and cisterns that hold it

Thirteen and a half drums, and three quarters of a cistern

A 55 gallon drum is the unit people picture, and one hundred cubic feet fills 13.6 of them, since 748.051948 / 55 = 13.6. A pallet of four drums holds 220 gallons, so the volume is a little over three pallets of drums. Stack them and the pile is taller than the drum buyer expects from a number that sounds small.

The 275 gallon IBC tote is the other common container: 748.051948 / 275 = 2.72 totes, so three totes take the whole load with 77 gallons of room left over. A 400 gallon spa is 53.4722 cubic feet, which means one hundred cubic feet fills 1.87 of them, and a 1,000 gallon cistern takes 133.6806 cubic feet, so the load covers 74.81 percent of that tank.

Small containers show the same total from the other end. The volume is 149.6 five gallon buckets, or 14.96 fifty gallon rain barrels, or 6,238.8 pounds of water at 8.34 pounds per gallon. A garden hose at 5 gallons a minute would run for 149.6 minutes to deliver it, which is two and a half hours of standing there.

Read the last column as a share when it drops below one. The cistern row means the load is three quarters of a fill, and the spa row means the tank runs over, which is the sort of check a hose and a clock settle faster than a calculation.

Three point seven yards is what the loader and the ticket use

Bags, scoops and a half empty truck

Bulk soil, mulch and gravel are priced by the cubic yard, so the order is written as 3.7037 yards. At $42 a yard the material costs $155.56. Add a flat $65 delivery and the ticket reads $220.56, which is the number to compare against bagged material at the same volume.

Bags are the other counter. One hundred cubic feet is 50 bags at 2 cubic feet, 33.33 bags at 3 cubic feet, and 134 bags at the 0.75 cubic foot size that holds about 40 pounds of soil. At $4.50 for a 2 cubic foot bag the same volume costs $225.00, so bulk material saves $69.44, and the delivered bulk total of $220.56 leaves $4.44 of that saving on the table.

A loader scoop is usually half a yard, or 13.5 cubic feet, so the pile takes 7.41 scoops. The last scoop is where yards differ: a careful operator weighs the seventh bucket rather than dropping an eighth full one. The bed of a 10 yard dump truck holds 10 yards level, so the load fills 37.04 percent of it, and that fraction is why a small order pays a haul charge that looks large next to the material.

The bag rows round up, which is why 33.33 bags of 3 cubic feet becomes 34 and 133.33 bags of 0.75 cubic feet becomes 134. Buying the rounded count always leaves a little material over, and running short by one bag means a second trip.

6,240 pounds of water, and the materials that weigh more

Payload, trailer rating and the ton per yard rule

Weight is where a volume stops being abstract. Water at 62.4 pounds per cubic foot makes one hundred cubic feet weigh 6,240 pounds. The more precise density of 62.366 pounds per cubic foot gives 6,236.6 pounds, and the gallons route at 8.34 pounds per gallon gives 6,238.8, so all three readings agree within four pounds.

That total is past the payload of a half ton pickup, which usually sits between 1,500 and 2,000 pounds, and past most single axle trailers rated at 3,500 pounds. A tank of this size belongs on a slab or on a trailer built for it. The same arithmetic explains why a 100 cubic foot aquarium is a structural question rather than a furniture question.

Material changes the total by a factor of four. Dry bark mulch runs about 25 pounds per cubic foot, so the load is 2,500 pounds. Damp topsoil runs near 75 pounds per cubic foot, which is 7,500 pounds. Sand runs about 100 pounds per cubic foot and gravel about 105, which put the same volume at 10,000 and 10,500 pounds and turn it into a dump truck job.

The working rule at a landscape yard is that a cubic yard of wet material runs about a ton, and 3.7037 yards is close to 3.7 tons. That rule is rough, and it is accurate enough to choose between a pickup, a trailer and a dump truck before anyone loads a bucket.

A meter reading of 1.03 therms, or 103,000 BTU

One hundred cubic feet, five appliances and a winter month

Natural gas is metered in cubic feet and billed in therms, and a therm is defined as 100,000 BTU. At 1,030 BTU per cubic foot, one hundred cubic feet carries 103,000 BTU, which is 1.03 therms. The shortcut that a therm equals 100 cubic feet is a rounding of the same fact, and the two readings differ by 3 percent.

The EIA heat content table puts U.S. residential deliveries at 1,031 BTU per cubic foot for 2024, and this page rounds that to 1,030 for clean arithmetic. Gas from a different basin carries a slightly different number, which is why a utility prints its own heat content factor on the bill.

Split the 103,000 BTU across the appliances in a house and the scale shows up. A 40,000 BTU per hour furnace burns it in 2.58 hours. A 22,000 BTU dryer takes 4.68 hours, a 12,000 BTU range top takes 8.58 hours, and a 250,000 BTU pool heater spends it in 0.41 hours, or 24.7 minutes. At $1.20 a therm the gas itself costs $1.24.

Turn the figure around and a heating bill makes sense. A cold month at 80 therms is 8,000,000 BTU, which is 7,767 cubic feet at 1,030 BTU per cubic foot, so one hundred cubic feet is 1.29 percent of the month. That is the honest size of a single reading on a meter that spins fast in January.

Boxes, a pallet and 2.8317 cubic meters

Cartons, dimensional weight and a container share

Freight moves in cubic feet and bills in pounds, and the two totals disagree at this volume. Start with cartons: a 12 inch cube is one cubic foot, so one hundred cubic feet is 100 boxes. An 18 by 18 by 16 inch carton measures 5,184 cubic inches, or 3 cubic feet, which gives 33.33 cartons. A 24 by 18 by 18 inch carton is 4.5 cubic feet and gives 22.22.

A pallet stacked 48 by 40 by 60 inches measures 115,200 cubic inches, or 66.67 cubic feet, so the load is 1.5 pallets. That half pallet decides whether a shipment rides at a pallet rate or pays a minimum charge, and it is the reason a seller pads a stack to a full 66.67 cubic feet.

Dimensional weight is the trap for light goods. Domestic air freight divides cubic inches by 139, so 172,800 / 139 = 1,243.2 pounds of billable weight on a load that may weigh 300 pounds on a scale. Density is the counterargument: 300 pounds in 100 cubic feet is 3 pounds per cubic foot, well under the 6 pound threshold most carriers treat as low density, so the dimensional figure wins.

Overseas the same volume is quoted in cubic meters. One hundred cubic feet is 2.8317 cubic meters, and a 20 foot container carries roughly 1,170 cubic feet of usable space, so the load is 8.5 percent of a box and rides as less than container load freight in a consolidation.

Paperwork follows the same numbers. A bill of lading lists the handling units, the freight class and whether the stop needs a liftgate, and a residential delivery without a dock adds a surcharge before anyone measures a box.

An inch and a half on a 20 by 40 pool

748 gallons of top off, and the same figure on a lawn

A 20 by 40 foot pool has 800 square feet of surface, and one inch of water over that surface is 800 / 12 = 66.6667 cubic feet, or 498.70 gallons. One hundred cubic feet therefore lifts the same pool by 1.5 inches, which is what a top off after a dry week looks like at the skimmer.

Smaller pools rise faster because the same volume spreads over less area. A 16 by 32 foot pool covers 512 square feet, so one inch is 42.6667 cubic feet and 319.17 gallons, and one hundred cubic feet is 2.34 inches. An 18 by 36 foot pool at 648 square feet takes 54 cubic feet per inch and 403.95 gallons, so the load lifts it 1.85 inches.

The lawn reads the same way. One hundred cubic feet spread over 1,000 square feet is 0.1 feet deep, which is 1.2 inches of water, or 748 gallons. An irrigation audit that measures 1 inch on a lawn is applying about 623 gallons per 1,000 square feet, and a hose that delivers 5 gallons a minute needs 124.6 minutes for that inch.

Pool chemistry runs the same refill figure from the other side. Backwashing a sand filter dumps water by the hundred gallons, and a partial drain to cut cyanuric acid can take a quarter of the pool. A leak that drops the level an inch a week is easier to catch when the gallon count per inch is already written on the wall beside the pump.

Rounding rules for a ticket and a bag count

Six decimals, four decimals and a whole bag

Gallons get six decimals because the ratio has them: 748.051948 reverses to 100.0000 when it is divided by 7.48051948051948. Cubic yards get four, because 3.7037 is close enough for a loader and precise enough for a ticket. Liters get four in the display and ten in the arithmetic, and the difference never moves a bag count.

Bag and carton counts always round up, and material sold by volume is billed by the yard as measured, not as rounded. A ticket that reads 750 gallons is 100.2604 cubic feet, a quarter of a cubic foot more than the round figure, which is within the tolerance of a tank gauge and well inside the error of a garden hose.

The one place rounding matters is a billing minimum. A yard that bills in half yard steps turns 3.7037 into 4 yards and adds $12.44 to the material line at $42 a yard. Ask which way the yard rounds before the truck leaves, because the same pile can be quoted at 3.5 yards by one seller and 4 yards by another.

The calculator at the top of the page repeats every figure above for any volume you type, in either direction. Nothing you enter leaves the browser, so a price test on a neighbor's load costs nothing and tells you whether the yard is quoting the same way twice.