How to check your propane tank level

Figures checked Nov. 10, 2026

On a big tank, read the gauge: it shows a share of the whole tank, so a full tank reads about 80%. On a cylinder, weigh it and take off the TW (tare weight) stamp; what's left is the propane in pounds. Type either into the calculator below to see the gallons.

Your tank	How to check it
Big tank, sized in gallons	read the gauge; full is about 80%
Cylinder, sized in pounds	scale reading minus the TW stamp = pounds of propane
Exchange cylinder, unopened	the net weight on the label

How much propane you have

The sums behind this tool are tested against 8 worked examples printed in published sources, and 34 checks in all, including the limits where it gives no number.

How to read a propane tank gauge

The gauge on a big tank shows a percentage of the whole tank, not of a full fill. Big tanks are filled to only about 80% of their size, so that is what a full tank reads. One propane supplier explains that a needle at 80% means the tank is completely full.

To get gallons, multiply the tank's size by the gauge reading. For example, say a tank of 500 gallons reads 40%: the calculator shows the gallons left. If your gauge reads above 80%, the calculator gives no number: ask your propane supplier or a certified propane technician.

How to check a cylinder by weight

Weighing is the method behind our calculator's cylinder sums. The propane weight page explains where the pounds-per-gallon figure comes from.

Weigh the cylinder on a scale that reads in pounds.
Find the TW (tare weight) stamp. That is the cylinder's empty weight.
Take the TW figure off the scale reading. The difference is the propane left, in pounds.
Divide by about 4.24 pounds a gallon for gallons, or let the calculator do it.

Exchange cylinders

An exchange cylinder's label gives the net weight of propane inside. One exchange brand fills its 20-lb grill tanks with a net weight of 15 pounds, not the full 20 lb.

If you don't know how a 20-lb cylinder was filled, the calculator uses that lower exchange fill and says so. Check the net weight on the label, or weigh the cylinder and subtract the TW stamp.

How to tell if a propane tank is empty

A cylinder is empty when the scale reading is down to its TW stamp. On a big tank, watch the gauge and don't let it run down: ask your propane supplier when to reorder.

We don't cover other home tricks for checking the level, because we found no official source for them.

How long will what's left last?

Once you know the gallons, the propane run time calculator shows how long they will run your appliances, from the Btu rating on each rating plate.

Questions people ask

Why does my full propane tank read 80%?

Big tanks are filled to about 80% of their size to leave room for expansion, so a full tank reads about 80%.

How do I know how much propane is in my grill tank?

Weigh it and take off the TW (tare weight) stamp. What's left is the propane in pounds; the calculator turns it into gallons.

What does TW mean on a propane tank?

Tare weight: the cylinder's weight when empty.

Before you light it

Carbon monoxide (CO) can kill. US Consumer Product Safety Commission (Official): “Fuel-burning heating systems, including furnaces and fireplaces, can produce CO, an odorless, colorless and deadly gas.” Source(opens in a new tab)
Fit CO alarms and test them. US Consumer Product Safety Commission (Official): “CO alarms should be placed on every level of the home and outside sleeping areas.” “Test the alarms every month to make sure they are working.” Source(opens in a new tab)
Have appliances checked every year. US Centers for Disease Control and Prevention (Official): “Have your heating system, water heater and any other gas, oil, or coal burning appliances serviced by a qualified technician every year.” Source(opens in a new tab)
Chimneys and vents too. US Fire Administration (Official): “Have chimneys and vents cleaned and inspected at least once a year.” Source(opens in a new tab)
If a CO alarm sounds (US: call 911): US Centers for Disease Control and Prevention (Official): “If the detector sounds leave your home immediately and call 911.” Source(opens in a new tab)
Know the signs. US Centers for Disease Control and Prevention (Official): “The most common symptoms of CO poisoning are headache, dizziness, weakness, nausea, vomiting, chest pain, and confusion.” Source(opens in a new tab)
Carbon monoxide (CO). CPSC (Official): "Fuel-burning heating systems, including furnaces and fireplaces, can produce CO, an odorless, colorless and deadly gas." "CO alarms should be placed on every level of the home and outside sleeping areas." Source(opens in a new tab)
If you smell gas (US: call 911). Connecticut Public Utilities Regulatory Authority (Official): "If the smell is strong or you are unsure, leave the building and then call." "Go to a phone that is not near the smell and call your propane company right away." "Don't smoke or strike any matches." "Don't flip light switches on or off." "Put out all open flames." "Call your propane company or 911 for help." This is general advice from one state's regulator: follow your own propane supplier's emergency instructions too. Source(opens in a new tab)
Keep propane cylinders outdoors. Utah State Fire Marshal (Official): "Never store a cylinder inside a house, building, or a garage." Source(opens in a new tab)
Outdoor-only heaters, grills and stoves stay outdoors. Mississippi State University Extension (Official), on outdoor-use-only heaters: "Never use them inside, even temporarily." Source(opens in a new tab)

Sources for this page

3 figures, each with its source

Every figure on this page, with its source. Open one to see the exact words on the source page and how it was checked.

Propane in a 20 lb exchange cylinder (net weight): 15 pounds of propane Other source
From Blue Rhino (exchange-cylinder maker): How much propane does Blue Rhino put in its tanks?, which says: “Blue Rhino propane grill tanks contain a net weight of 15 lbs. of propane.” Open the source (opens in a new tab)
Checked Nov. 9, 2026.
Weight of a gallon of propane: 4.24 pounds per gallon Other source
From U-Haul (retailer): 20-lb Steel Propane Tank product page (answer in the page's customer Q&A, 2021), which says: “The Propane that should be going into this tank only would weigh about 4.24lbs per gallon of propane.” Open the source (opens in a new tab)
Checked Nov. 10, 2026. A second check re-opened the source page and matched it on Nov. 9, 2026. A blind check looked it up again on Nov. 10, 2026 without seeing our figure: it didn't find a better source, so this figure stands.
Maximum fill of a propane tank: 80% Official
From Utah State Fire Marshal: LP-Gas Basic Filling Procedures, which says: “To allow for expansion, propane containers are to be filled only to 80% of their capacity.” Open the source (opens in a new tab)
Checked Nov. 9, 2026. A second check re-opened the source page and matched it on Nov. 9, 2026. A blind check looked it up again on Nov. 10, 2026 without seeing our figure: the two agreed.