How Many Gallons In a 20 lb Propane Tank (Propane Tank Sizes)

How Many Gallons In a 20 lb Propane Tank

Have you ever asked yourself or your friend how many gallons are in a 20 lb propane tank? Well, you are at the perfect place to find the answer to such a question.

A 20 lb propane tank holds 20 lb of propane, right? Well, not exactly.

Yep, it can be quite confusing! But, don’t worry; we’re going to make it as simple as possible to understand.

So, how many gallons in a 20 lb propane tank? Theoretically, you can get between 4.7 and 5 gallons of propane into an empty 20 lb propane tank, but that is not safe. In reality, a 20-lb propane tank is about 80% full, so the most you can put in is 4 gallons.

How Many Gallons In a 20 lb Propane Tank?

Generally speaking, you can get 4 gallons of propane in an empty 20 lb propane tank. However, that’s not its maximum capacity.

Instead, 4 gallons is about 80% full. At maximum capacity, you can fit between 4.7 to 5 gallons, but this is not safe.

Why Is Filling It Up Over 80% Unsafe?

It’s all about temperature and pressure!

As the temperature increases, the propane inside your tank expands. The 20% of space ensures it can grow safely. When overfilled, it can rupture during expansion which is a grave threat to life.

The growing temperature impacts the pressure inside the tank. At 30 degrees F, it sits at around 60 psi; at 100 degrees F, it can reach 200 psi. 

Read also: How To Store Propane Tanks In Hot Weather

Overfill Protection Device

If you’re a tad scared about overfilling your 20 lb propane tank now, it’s understandable. But, you’re in good hands as all legal tanks come with an OPD (Overfill Protection Device).

It’s essentially a float that shuts the valve when it reaches 40 to 4.2 gallons of propane.

A good way to check whether your tank has an OPD is to open the valve. If you release it and propane starts coming out, you don’t have an Overfill Protection Device.

Sometimes, you might be able to tell by simply looking at the top of the valve. If there’s a triangular handwheel, your tank has an OPD. 

Propane Pounds Per Gallon Chart

It’s worth understanding propane’s pound per gallon ratio when considering how many gallons fit in a 20 lb propane tank. Consult our handy chart below to find out more:

Pounds Gallons

How to Gauge How Much Propane Is Left in Your Tank

You now know how much propane a 20 lb tank can hold. But how do you figure out how much is left in yours?

Thankfully, it’s easy than it might seem. Just use one of our top four methods below (some are more accurate than others):

#1 Use Hot Water

Using hot water is unarguably the quickest way to approximate the level of propane in your tank. Follow these steps:

  1. Fill a small bucket or cup with hot water. No need to boil a kettle; just use the hottest setting on your tap.
  2. Pour the water over the side of your tank.
  3. Use your hand to feel for a cool section. The top of the cool section is the fill level!

The propane absorbs the heat from the water, making the outside feel cool. Of course, it’s not an accurate measurement.

But it’s more than enough to tell you whether you need to head to the store before you start grilling.

#2 Measure Cook Time

Running out of gas during your grill session probably isn’t your idea of a good time. So, using a little bit of math can help estimate how long your tank should last.

Use our step-by-step guide below:

  1. One gallon of propane gives around 92,000 BTUs.
  2. Divide that by your grills BTUH (BTUs per hour). That equals the amount of time it takes your grill to use a gallon of propane at maximum heat.
  3. Multiply the number of hours by the gallons in your tank. 

Again, it’s still only an approximation. But it’s rather helpful to keep on top of your cooking time and heat control.

#3 Use Weight

If you’re used to dealing with propane tanks, you can tell whether you need to refill it by simply holding it. But, you need a scale to get a more accurate picture of the remaining gas level.

To measure the pounds of propane left inside, weigh the tank and minus the tare weight. The answer to that calculation equals the number of pounds of propane remaining.

#4 Buy a Proper Gauge

When precision is vital, it’s prime time to invest in a dedicated gauge. Several types exist and can be found easily at your nearest hardware store:

  • Analog Propane Scales — They work similarly to luggage scales. However, they’re already calibrated to the weight of the thank. Simply thread the hook through the thank’s handle, pick it up, and read the gas level.
  • Inline Pressure Gauges — With this type, you need to connect it between your grill’s gas line and the cut-off valve on your tank. They use pressure to measure the propane level and give you a warning when you’re running low.
  • Digital Propane Scales — These constantly weigh your tank and give you a digital reading of the remaining gas percentage and cook time.

What Size Propane Tank Do You Need?

So, is your 20 lb propane tank big enough? You may have found that you need more than 4 gallons of propane. In which case, no, your 20 lb tank is not big enough.

But luckily, they come in all shapes and sizes. You can even find tanks that hold over 2,000 gallons!

Ultimately, the size you need depends on the size of your house, as well as the size and number of appliances requiring propane. Plus, your area’s climate and location can dictate how much propane you need.

We suggest following this size guide:

  • 20 lb Tanks — For propane grills, patio heaters, generators, and similar outdoor equipment.
  • 120 Gallon Tanks — For one to two residential appliances like water heaters and stoves.
  • 250 Gallon Tanks — For two home appliances like pool heaters and water heaters.
  • 500 Gallon Tanks — For home heating or households with up to three propane appliances.
  • 1000 Gallon Tanks — For heating larger homes or families running all appliances on propane.

Read also: Does Costco Refill Propane Tanks (6 Filling Stations)

The Bottom Line

Sticking to the 4-gallon guideline when filling up your 20 lb propane tank ensures you and your loved ones are safe and sound! 

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Mike Gilmour

Hi, I'm Mike, co-founder, and editor of RV and Playa. My passion is traveling (with my RV) and enjoying the day at the beach (Playa)! Well, I originally created this blog as a way to share what I've learned by experimenting with the RV lifestyle, and I want to help others develop in life through new skills and opportunities.

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