What it costs to fill a propane tank, 80 % rule included
A 500-gallon tank at 30 % takes 250 gallons to reach 80 %, about $672 at this week's U.S. average.
Cost to fill your propane tank
$609
| Gallons the delivery adds | 250 gallons |
| Michigan average, October 19, 2026 | $2.434/gal |
| Same fill at last year's price ($2.161) | $540 |
| Full tank from empty, same price | $974 |
Propane tanks are never filled to the top: federal rules cap a home tank at 82.4 % to 83.3 % of its volume (29 CFR 1910.110, Table H-27). EIA weekly survey of October 19, 2026, excluding taxes. Next release October 28, 2026.
Compiled by Radif Partners · Where the prices come from · EIA weekly survey of October 19, 2026, excluding taxes · no dealer listed
A propane tank is never filled to its nominal size. Federal rules for aboveground home tanks of up to 1,200 gallons cap the fill at 42 % of the weight of water the tank holds, which for propane is 82.4 % to 83.3 % of the tank's volume, and a filled tank commonly reads about 80 % on its gauge. So a 500-gallon tank holds about 400 gallons of propane at most, and a delivery adds the gap between your gauge and 80 %: from 30 %, that is 250 gallons. At the U.S. average of $2.689 a gallon in the federal survey of October 19, 2026, the fill costs $672 before tax; a full fill from 10 % is $941. Several price pages online multiply the nominal size by the price and overstate the bill by a fifth or more. The calculator applies the rule, starts from your state's average and takes your dealer's price when you have it.
The rule behind the 80 %
Propane is stored as a liquid under pressure, and the liquid expands as it warms. A tank filled to the top on a cold morning could reach its relief valve on a hot afternoon. The federal rule on the storage of liquefied petroleum gas (29 CFR 1910.110, Table H-27) therefore limits the "filling density", the weight of gas in the tank as a share of the weight of water the tank would hold at 60 °F. For an aboveground tank of up to 1,200 gallons and propane with a specific gravity of 0.504 to 0.51, the cap is 42 %. Divide by the specific gravity and the liquid takes 82.4 % to 83.3 % of the tank's volume. Drivers stop a little under that ceiling, and a filled tank commonly shows about 80 % on its gauge: the level the calculator starts from, which you can change to what your ticket shows.
The practical consequence: a tank's usable size is about four fifths of its nominal size.
| Tank size | Holds at 80 % | Fill from 20 % | Cost from 20 % | Fill from 30 % | Cost from 30 % |
|---|---|---|---|---|---|
| 120 gallons | 96 gal | 72 gal | $194 | 60 gal | $161 |
| 250 gallons | 200 gal | 150 gal | $403 | 125 gal | $336 |
| 500 gallons | 400 gal | 300 gal | $807 | 250 gal | $672 |
| 1,000 gallons | 800 gal | 600 gal | $1,613 | 500 gal | $1,345 |
Reading the gauge
Unlike an oil gauge in fractions, a propane gauge reads in percent of the tank's volume. Gallons in the tank = size × reading. A 500-gallon tank at 30 % holds 150 gallons; filled to 80 %, 400. The delivery adds the difference. If your delivery ticket shows more gallons than the gap between the two readings allows, ask the dealer how the gauge was read.
Your tank, your gauge
Cost to fill your propane tank
$669
| Gallons the delivery adds | 275 gallons |
| Michigan average, October 19, 2026 | $2.434/gal |
| Same fill at last year's price ($2.161) | $594 |
| Full tank from empty, same price | $974 |
What the state changes
Propane prices vary more between states than heating oil. This week a 250-gallon fill costs $413 at the North Dakota average and $1,232 at the Florida average. The spread is not in the gas: wholesale propane is close to the same price everywhere. It is in what the dealer adds for delivery, storage, the tank and its own margin. The state table ranks every surveyed state.
Owned tank or leased tank
Many homes lease the tank from the dealer that fills it. The lease usually ties the deliveries to that dealer, so the price per gallon is not shopped from week to week; the state average is then a check rather than a choice. A household that owns its tank can call any dealer, and the gap between its quote and the state line tells it whether to keep calling. Either way, the tank rental and any minimum-use fee are billed apart from the gallons and do not show in the survey.
A winter's worth of fills
The EIA's average propane-heated home burns 494 gallons from November to March nationwide, 641 gallons in the Midwest and 515 gallons in the Northeast. With a 500-gallon tank holding about 400 gallons usable, a Midwest home needs at least two fills over the winter on top of what is in the tank in November. The winter budget scales those gallons to your state, and the days-left calculator works for propane too.