How to Read a Propane Tank Gauge

Propane is delivered and stored as a liquid. However, propane boils at a temperature of -44°F, so inside the truck and tank that liquid is boiling and turning to vapor (or gas). Propane gas has a greater volume than propane liquid and so requires more space to contain it. Because of this, a propane tank is never filled to 100% – there must always be space into which the liquid propane can evaporate, creating a pocket of gas at the top of the tank. This is the gas that will be used when you open a valve on an appliance in your home. As the gas is drawn off, so the liquid within the tank boils faster and more gas is produced to replace the old.

On top of a propane tank you will see a fill pipe, a shut-off valve, an emergency vent, a gauge showing how much liquid propane is in the tank, and possibly a regulator valve (if it is not on top of the tank itself it will be located next to the tank and will be connected to the valve via a copper, iron or special plastic pipe).

lamprey energy how to read a propane tank

Top of propane tank, clockwise from far left: Fill (yellow), regulator (red) connected to the valve with shut-off (Grey), emergency vent (green), Gauge (bronze).

Gauge showing tank at 55% full – on a 500-gallon tank this means the tank currently holds 275 gallons.

Gauge showing tank at 55% full – on a 500-gallon tank this means the tank currently holds 275 gallons.

The tank gauge shows what percentage of the tank’s capacity is full. (Remember it will never read 100% – full will be 80%.) Thus, if you have a 1000-gallon tank and the gauge reads:
80% (full), you have 800 gallons of propane
50% you have 500 gallons of propane
30% you have 300 gallons of propane and should order more
10% you have 100 gallons of propane

If you have a 500-gallon tank and the gauge reads:
80% (full), you have 400 gallons of propane
50% you have 250 gallons of propane
30% you have 150 gallons of propane and should order more
10% you have 50 gallons of propane

If you have a 120-gallon tank and the gauge reads:
80%, you have 96 gallons of propane
50% you have 60 gallons of propane
30% you have 36 gallons of propane and should order more
10% you have 12 gallons of propane

Gauge showing tank at 55% full – on a 120-gallon tank this means the tank currently holds 66 gallons.

Gauge showing tank at 55% full – on a 120-gallon tank this means the tank currently holds 66 gallons.

If you’re not on automatic delivery, it’s time to reorder when your gauge reads 30% of less. And even if you are on automatic delivery, it’s good to know where your gauge is and how to read it – perhaps you’ve switched on a pool heater and haven’t told us, or maybe you ran your propane-fired generator for a few days…whatever the reason, if there’s a spike in your consumption caused by anything more than just a drop in outdoor temperature, check your gauge and give us a call at 603.964.6703 if you’re at 30% or less.

Comments 11

  1. Tara Allen

    I like knowing that there are easy ways to check your propane gauge. I did not realize that propane can evaporate. That is nice that propane can be delivered easily in it’s liquid state.

  2. Judy Wilson

    Thanks for posting this information for reading a propane tank gauge. I’m having one installed in my home soon, so it seems important for me to know how to read the gauge. The tank that I’m considering installing is a 500-gallon tank, so I should keep in mind that seeing the marker at 80% full means that there’s 400 gallons of propane left. I’ll use this as a reference in the future to make reading the gauge easier.

  3. David Duncan

    Hi, I have a 5000 Liters bulk tank use for commercial use. When my supplier refill me, I never get out the amount of propane paid for according to my meter reading. What do think is the problem?

  4. Faylinn

    I’m going to be using my grill tonight to cook dinner for my kids and I have never done that without my husband before and so I know nothing about how to read a propane tank gauge. However, I am really glad that described how many gallons each percentage has. I have a 120-gallon tank and I think that it is at 15%, which then means that it has about 18 gallons in it. Do you think that 18 gallons is enough to cook a few steaks on a grill?

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  5. Jack Mulligan

    I didn’t know that propane gas acted so strangely and is never filled to 100% in the tank. I always wondered how it functioned as a gas when it’s transported as a liquid. It’s kind of cool that it self regulates inside the tank as long as it’s under the right amount of pressure.

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  6. Kate

    I just got a propane delivery and the gauge says 90%!! Is this ok or is this dangerous? I have been in this house for 3 years and NEVER had a reading of 90%.

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  7. Mary

    We have a tank at 40% I. Our home. The provider could not make it for delivery due to a storm. How long will this last for hot water tank and dryer that use it. Thank you

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