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4 ways to estimate how much propane you have left

Never again run out of propane in the middle of your BBQ with these easy methods.

Quirky

It's finally summer, which means it's time to break out the grill, give it a thorough cleaning, slap some patties on it, and have your first backyard cookout of the year. But how do you know how much propane is left in the tank? Most propane tanks don't come with a gauge to let you know how much fuel is remaining. And you definitely don't want to run out and have to make a trip to the store in the middle of cooking.

Fortunately, there are a few ways to quickly check the level of propane before firing up the grill. Here's how it's done.

Once you've got your propane topped up, you can learn to grill smarter this summer with CNET's guide to grilling.

With hot water

One of the quickest ways to approximate the fill level of a propane tank comes from the "Fix It Home Improvement Channel" over on YouTube. All you need is a bit of hot water.

  • Fill a cup or a small bucket with hot water from the tap.
  • Pour the water down the side of the tank.
  • Run your hand down the side of the tank and feel for a cool spot.

The top of the cool spot is the fill level of the tank. What's happening here is the liquid propane inside the tank is absorbing the heat from the water, which makes the metal wall of the tank cool to the touch, whereas the tank wall above the fill line will be warm.

This doesn't give you a very accurate measure of how much propane is left, but rather a decent approximation. It's certainly enough to let you know whether or not you should head to the store before starting to cook.

More on Chowhound: What's the difference between barbecuring and grilling?

By weight

If you've been dealing with propane tanks for a long time, you can approximate whether it's time to get it refilled simply by picking it up. But to get a better idea of how much gas is remaining, you will need a scale.

All propane tanks come with a few numbers stamped on the handle -- most commonly the WC (water capacity) and TW (the weight of the tank when it's empty). Most propane tanks for grilling weigh around 17 pounds (8 kilograms) when empty and hold roughly 20 pounds (9 kilograms) of propane.

To measure how many pounds of propane are remaining, weigh the tank and subtract the tare weight. For instance, if you weigh the tank and have 27 pounds (12 kilograms) total and have a tare weight of 17 pounds (8 kilograms), you have 10 pounds (4.5 kilograms) of propane -- approximately half a tank -- remaining.

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By cook time

A little math goes a long way in being able to estimate how long one propane tank will last. First, consider that one gallon (3.8 liters) of propane produces approximately 92,000 BTUs. Divide that number by the BTUH (BTUs per hour) rating of your grill. This leaves you with the number of hours it will take for you to use one gallon of propane at the grill's maximum heat setting.

Finally, multiply the number of hours by the number of gallons in the tank. A full 20-pound (9-kilogram) propane tank holds 4.7 gallons (17.8 liters) of propane. If your grill has an output of 32,000 BTUH, you would get approximately 13.5 hours of cook time out of a standard propane tank if you were cooking at maximum heat. If you're only using two out of four burners, you could estimate that the approximate cook time would be double.

While this method is still just a rough approximation, it's helpful to keep track of cook times and heat settings. But if you forget to write it down somewhere, you can pair this method with one of the two above methods to calculate roughly how much cook time is left in a tank. For instance, if you weigh a tank and have 10 pounds (4.5 kilograms) of propane left, you would have approximately 6.75 hours of cook time left in the tank at full heat.

Buy a gauge

When approximate numbers just won't do and you need precision, it's time to invest in a gauge. Propane tank gauges come in several different forms and are easily found at your hardware store.

  • Inline pressure gauges install between the gas line from the grill and the cut-off valve on the tank. These gauges work on pressure and give a readout letting you know when the tank is full, low or empty.
  • Analog propane scales work much like luggage scales, except they're already tared for the for the weight of the tank. Slip the hook through the handle of the tank, pick up and read the remaining gas level.
  • Digital propane tank scales work by constantly weighing the tank and provide a digital readout of remaining cook time and gas fill percentage.

These gauges and scales range from about $10 (approximately £10 or AU$15) to $50 (about £35 or AU$65) and might prove useful if you do a lot of cooking on the grill.

How to grill smarter: Consider this your guide to cooking like a pro at your next BBQ.

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