# 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:

[ Read: How many gallons of propane in a 20 lb tank ]

### 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