How many gallons a propane tank takes
Propane tanks are sized by water capacity, and they are not filled to the top. OSHA's LP-gas rule limits every fill by "filling density" and requires a fixed liquid-level gauge on each container filled by volume, with the percentage full that gauge shows marked beside it.[osha110] State fire marshal procedures fill containers to 80% of capacity to leave room for the liquid to expand as it warms.[utfm] So a 500 gallon tank holds about 400 gallons, and the gauge reading is a percentage of the 500 gallons, not of the 400.
| Tank size | Empty → 80% | Cost | 20% → 80% | Cost | 20% → 80% in Iowa | 20% → 80% in Florida |
|---|---|---|---|---|---|---|
| 100 gallons | 80 gal | $226.08 | 60 gal | $169.56 | $110.94 | $306.36 |
| 120 gallons | 96 gal | $271.30 | 72 gal | $203.47 | $133.13 | $367.63 |
| 250 gallons | 200 gal | $565.20 | 150 gal | $423.90 | $277.35 | $765.90 |
| 320 gallons | 256 gal | $723.46 | 192 gal | $542.59 | $355.01 | $980.35 |
| 500 gallons | 400 gal | $1,130.40 | 300 gal | $847.80 | $554.70 | $1,531.80 |
| 1,000 gallons | 800 gal | $2,260.80 | 600 gal | $1,695.60 | $1,109.40 | $3,063.60 |
The formula is gallons = tank size × (fill limit − gauge reading) ÷ 100, and cost = gallons × price per gallon + any delivery fee. Each 10% on a 500 gallon tank's gauge is 50 gallons, about $141 at this week's U.S. average.[shopp_lp]
Cost to fill a 500 gallon propane tank by state
The same 300-gallon top-off costs $555 in Iowa and $1,532 in Florida at this week's survey prices.[shopp][shopp_lp] States EIA surveys, cheapest first:
| State | Price per gallon | 20% → 80% (300 gal) | Empty → 80% (400 gal) | Price vs year earlier |
|---|---|---|---|---|
| Iowa | $1.85 | $554.70 | $739.60 | +20% |
| North Dakota | $1.85 | $555.60 | $740.80 | +18% |
| Nebraska | $1.88 | $564.90 | $753.20 | +19% |
| Illinois | $2.01 | $602.10 | $802.80 | +16% |
| South Dakota | $2.06 | $616.80 | $822.40 | +19% |
| Wisconsin | $2.15 | $645.00 | $860.00 | +23% |
| Minnesota | $2.19 | $657.30 | $876.40 | +18% |
| Kansas | $2.30 | $688.80 | $918.40 | +26% |
| Missouri | $2.37 | $710.70 | $947.60 | +20% |
| Montana | $2.37 | $710.70 | $947.60 | +25% |
| Colorado | $2.45 | $733.50 | $978.00 | +16% |
| Oklahoma | $2.47 | $740.10 | $986.80 | +15% |
| Michigan | $2.53 | $758.40 | $1,011.20 | +16% |
| Utah | $2.57 | $771.90 | $1,029.20 | +15% |
| Arkansas | $2.59 | $777.60 | $1,036.80 | +15% |
| Indiana | $2.75 | $824.10 | $1,098.80 | +21% |
| Idaho | $2.78 | $832.50 | $1,110.00 | +20% |
| Ohio | $2.82 | $847.20 | $1,129.60 | +16% |
| Kentucky | $2.93 | $878.70 | $1,171.60 | +16% |
| Texas | $3.20 | $959.70 | $1,279.60 | +9% |
| Mississippi | $3.20 | $960.30 | $1,280.40 | +7% |
| Pennsylvania | $3.33 | $999.60 | $1,332.80 | +17% |
| Georgia | $3.37 | $1,010.70 | $1,347.60 | +13% |
| Tennessee | $3.42 | $1,025.40 | $1,367.20 | +12% |
| Maine | $3.69 | $1,105.50 | $1,474.00 | +17% |
| Alabama | $3.70 | $1,110.90 | $1,481.20 | +7% |
| North Carolina | $3.73 | $1,119.30 | $1,492.40 | +13% |
| Virginia | $3.80 | $1,140.00 | $1,520.00 | +12% |
| New York | $3.81 | $1,142.10 | $1,522.80 | +12% |
| Massachusetts | $3.84 | $1,152.60 | $1,536.80 | +16% |
| Maryland | $3.93 | $1,178.10 | $1,570.80 | +11% |
| New Hampshire | $3.94 | $1,182.30 | $1,576.40 | +14% |
| Delaware | $3.95 | $1,183.50 | $1,578.00 | +14% |
| Vermont | $3.99 | $1,198.20 | $1,597.60 | +11% |
| Rhode Island | $4.06 | $1,218.90 | $1,625.20 | +16% |
| New Jersey | $4.13 | $1,239.90 | $1,653.20 | +17% |
| Connecticut | $4.43 | $1,329.30 | $1,772.40 | +19% |
| Florida | $5.11 | $1,531.80 | $2,042.40 | +10% |
Price per gallon for every surveyed state, with last season's averages, is on propane prices.
Propane price per gallon this heating season
The U.S. residential price was $2.83 a gallon in the week of Nov 9, 2026, +15% from $2.45 a year earlier. Last season it ranged from $2.42 to $2.68, so the same 400-gallon fill would have cost $967 to $1,071 at last season's weekly low and high.[shopp_lp]
How much heat a tank of propane holds
A gallon of propane holds 91,452 Btu.[btu] A 400-gallon fill is 36.6 million Btu, and a 95% AFUE furnace turns that into about 34.8 million Btu of heat, the same heat as 366 therms of natural gas burned in that furnace. A home that burns 800 gallons over a winter needs two such fills. To see whether a heat pump or another fuel would heat the same home for less, use heat pump vs furnace cost; the cost of a whole winter of propane is on heating oil prices for oil homes and natural gas prices for gas.
What else is on a propane delivery bill
- Price per gallon. The EIA figure is an average of residential prices dealers report each week; your quote depends on the dealer, the contract and the size of the delivery.[shopp]
- Delivery or small-fill fees. Any flat charge on the ticket, such as a fee for a small or off-route delivery, raises the real price per gallon. Enter it in the fee field above and the calculator shows the all-in figure.
- Tank rental or lease. If the dealer owns the tank, any rental charge is billed apart from the gallons and is not part of the per-gallon price.
Frequently asked questions
How much does it cost to fill a 500 gallon propane tank?
About $1,130 from empty (400 gallons, an 80% fill) at the U.S. average of $2.83 per gallon in the week of Nov 9, 2026, or $848 to top it up from 20% to 80%.
How many gallons does a 500 gallon propane tank hold?
About 400 gallons. Tanks are filled to 80% of their water capacity so the liquid has room to expand.
How do I read a propane tank gauge?
The gauge shows the percentage of the tank's water capacity that is full. On a 500 gallon tank, 30% means about 150 gallons are left, and filling to 80% adds 250 gallons.
What is the cost to fill a propane tank in my state?
Pick your state in the calculator. This week a 300-gallon top-off ranged from $555 in Iowa to $1,532 in Florida.
Sources
- Heating Oil and Propane Update (weekly residential prices; collected October through March)
- Weekly Propane Residential Price by state (dollars per gallon)
- 29 CFR 1910.110(b)(12) and (b)(19), Storage and handling of liquefied petroleum gases: maximum permitted filling density (Table H-27) and the fixed liquid-level gauge marked with the percentage full
- LP-Gas Basic Filling Procedures (containers filled only to 80% of capacity to allow for expansion)
- British thermal units (Btu): heat content of electricity (3,412 Btu/kWh), natural gas, heating oil (138,500 Btu/gal) and propane (91,452 Btu/gal)