How to tell how much propane is left in a tank
Updated October 24, 2026
Grill cylinders have no fuel gauge. The three checks below take under a minute and need nothing more than a bathroom scale or a cup of warm water.
Weigh it
Every cylinder has its empty weight stamped on the collar after the letters TW (tare weight), usually 17 or 18 lb. Put the tank on a bathroom scale and subtract the tare weight. What is left is propane.
- 20 lb: full
- 10 lb: half
- 5 lb: about three hours of grilling on a two-burner at medium
- Under 2 lb: refill before the weekend
This is the same method a refill station uses, so it is also the way to check that a fill was complete.
Warm water
Pour a cup of warm tap water down one side of the tank, then run a hand down the same line. Liquid propane absorbs heat, so the steel stays cool where there is propane and warms where there is only vapor. The line between warm and cool is the fill level. It works best on a warm day and on a tank that has been sitting still.
Inline gauge
A pressure gauge screwed between the tank valve and the regulator hose shows green, yellow or red. It measures pressure, which stays almost constant until the tank is nearly empty and drops with cold weather, so treat it as a low-fuel warning rather than a fuel level.
What a fill should weigh
A refill brings the tank to 20 lb of propane, so a 17 lb tank should weigh about 37 lb on the way home. Exchange tanks are usually filled to 15 lb; the sleeve says so. If a refill comes up short, say so at the counter; stations fill by weight and can top it off.
When it is time to fill, the station finder sorts refill stations by distance from your ZIP code.