How To Tell How Full (or Empty) Your Propane Tank Really Is

Nearly everyone has the typical 20-pound (5-gallon) barbecue grill propane tank. But, how do you know how empty or full your propane tank really is?

How much does an EMPTY propane tank weigh?

Answer: An empty propane tank will weigh the “TW” (Tare Weight) value listed on the tank’s collar. I have 4 tanks of this size . Two of them are stamped 18 pounds, the other two are stamped 16.6 pounds (about 17 pounds average empty weight). Your tank may vary slightly. Read on for more detail.

How much does a (safely) FULL 20-pound propane tank weigh?

Answer: A standard 20 pound propane tank when safely full (80% full) , weighs the stamped “TW” (Tare Weight) plus 16.8 (the weight of 4 gallons of propane.. 4 x 4.2 LBS per gallon). So 17 + 16.8 = 33.8 pounds when full (again, depends on your tank Tare Weight so check the collar stamp).

Do they ever really fill a 20 pound propane tank all the way?

No, they don’t. Propane expands with heat. Therefore there’s a safety margin which limits a tank to only fill 80% full.

This is where your ‘mileage may vary’. It comes down to a safety margin. Standard ‘BBQ’ 20 pound propane tanks have a built-in Overfill Protection Device valve. It acts like a float, and will close the valve when it reaches 4.0 – 4.2 gallons. So at most, you’re going to get about 4 gallons of propane in a full tank. But do they even fill it to that level?

I own all of my own tanks (rather than the trade-ins). So I get them filled at my local hardware store. Their standard operating procedure is 3.8 gallons to ‘fill’ it. Other people may have different experiences with how much they get at a propane refill station..

Propane Tank Weight | Calibrated Gauge

Here’s a quick and easy way to know how full your propane tank really is. Use a weight gauge that’s specifically calibrated for the typical 20 pound BBQ-size propane tank. None of us need to be exact here. Instead we’re just looking for a reasonable approximation of how full or how empty..

Hook, Lift, and Look:

Hanging Gauge Scale
(view on amzn)

The following is a new Propane Scale product since my original post which I will include in this update..

It’s a propane tank digital scale for 5LB, 10LB, 20LB, 30LB, or 40LB tanks. There’s simply a button on the top to select your tank size. Might be useful if you have more than just a typical 20 pound propane tank. Maybe you have a 30 pound RV tank too (for example).

Flame King Scale
(amzn)

Weigh The Propane Tank Yourself And Do The Math..

Alternatively you could weigh your own propane tank with an ordinary hanging scale or by setting it on a floor scale. As explained above, there’s a little math involved, but it’s no big deal.

Hanging Weight – Tare Weight (“TW” printed on tank collar) = pounds of propane inside

(propane weighs ~4.2 pounds per gallon)

Here’s the most accurate way to find out how much propane is in your tank:

First, you might use this multipurpose luggage scale:

LUGGAGE SCALE
(view on amzn)

All propane tanks have 2 weights stamped onto the top handle (the collar)

– One is the tank’s empty weight (“TW” – Tare Weight)

– The other is its full weight (“WC” – full with WATER… not propane… see below)

TW (Tare Weight)

This is the weight of the tank itself when empty.

WC (Water Capacity)

This is the weight of the water required to fill the tank (yes, water).

The typical 20-pound (5-gallon) size barbecue grill tank will hold 47.6 pounds of water.

Regulations limit the propane level to not exceed 42% of the water capacity of the tank.

Long story short – Regulations require the maximum weight of propane in a typical barbecue grill tank to be no more than 42% of 47.6, or 20 pounds.

4 Gallons of Propane is Full, Not 5 gallons

80% is now considered “FULL” due to safety reasons. Refill stations will only fill a 20 lb propane tank to 80% of it’s maximum, or 4 gallons instead of 5 gallons. Here’s more about it and why they do that:

Subtract Tare Weight From Measured Weight

So, what do we do with this information regarding a propane tank’s ‘Tare’ weight?

How do you actually discover how empty or full your propane tank is?

Simply weigh your propane tank and subtract it’s “Tare Weight”

American Weigh Scale
(view on amzn)

You can use any scale. A floor scale, or a hanging scale. There are several hanging scales on the market. I’ve been using the one picture above for my 20 & 30 pound portable propane tanks (bbq and RV).

For example, I just weighed my bbq grill tank and it weighs 32.6 pounds. The Tare Weight stamped on the collar is 16.6 pounds.

32.6 – 16.6 = 16 pounds of propane

20 pounds is considered maximum regulation full.
In my example, 16 pounds is 4/5 full, or 80%.

Propane weighs 4.25 pounds per gallon.

Tip! Depending on the weather conditions you may actually see condensation on the sides of a propane tank. There will be a clear demarcation indicating the level of propane inside the tank!

Here’s a chart where you can check the stamped W.C. on your propane tank and cross reference the maximum pounds of propane that will fill it. A typical bbq tank will be stamped 47.6 or 47.8.

Propane Cylinder (Tank) Filling Chart

“WC” versus Maximum Pounds of Propane

2.39 — 1
4.78 — 2
7.17 — 3
9.56 — 4
11.9 — 5
14.3 — 6
16.7 — 7
19.1 — 8
21.5 — 9
23.9 — 10
26.2 — 11
28.6 — 12
31.0 — 13
33.4 — 14
35.8 — 15
38.2 — 16
40.6 — 17
43.0 — 18
45.4 — 19
47.8 — 20 (typical bbq grill size tank)
59.7 — 25
71.7 — 30 (my RV tank size)
78.8 — 33
83.6 — 35
95.6 — 40
105.1 — 44
119.5 — 50
239.0 — 100