How to Determine Your Propane Tank Size

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Quick answer

• Your RV or camper propane tank size is usually stamped on the tank itself.
• Look for the water capacity in gallons or pounds.
• Common sizes are 20lb (5-gallon) and 30lb (7.5-gallon).
• Larger RVs or those with more appliances might have 40lb (10-gallon) or even bigger tanks.
• If you can’t find it on the tank, check your RV’s manual or the manufacturer’s specs.
• Knowing your tank size helps you plan refills and understand how long your fuel will last.

What to check first (do this before you drive out)

Before you hit the road, a little prep goes a long way. Knowing your propane tank size is key to a smooth trip.

• Tank Markings: Your propane tank should have its capacity stamped directly on it. This is usually in pounds (lbs) or gallons. For example, a common “20 lb” tank holds about 5 gallons of propane. Don’t sweat it if the numbers aren’t super obvious; they’re usually near the valve or on a collar.

• RV/Camper Manual: If the markings are worn off or hidden, your vehicle’s owner’s manual is your next best bet. It should detail the original equipment, including propane tank sizes. The manufacturer’s website might also have this info if you know your RV’s model and year.

• Appliance Needs: Think about what you use propane for. Do you just need it for a stove and a water heater? Or are you running a furnace, fridge, and maybe a grill too? More appliances mean you’ll likely have larger or multiple tanks. This helps you gauge if your current setup makes sense.

• Refill Station Availability: Knowing your tank size helps you estimate how much propane you’ll need and how often you’ll have to stop for refills. Some remote campgrounds might have limited refill options, so planning ahead is smart.

Step-by-step (field workflow)

Here’s how to nail down your propane tank size when you’re out and about.

1. Locate the Tank(s): Find where your propane tank(s) are stored. They’re usually in a dedicated compartment, often at the front of an RV or on the tongue of a travel trailer.

• Good: You can easily see and access all your propane tanks.
• Mistake: Forgetting you have a secondary tank or one hidden away. Always check all of them.

2. Inspect the Tank Surface: Get close and look for any stamped information. You’re hunting for numbers followed by “LB” (pounds) or “GAL” (gallons).

• Good: Clear markings showing “20 LB” or “7.5 GAL”.
• Mistake: Assuming the tank is empty or full based on its weight. Weight is only a rough indicator; markings are definitive.

3. Identify the Capacity: Note down the size indicated. The most common sizes are 20 lb (holds about 5 gallons) and 30 lb (holds about 7.5 gallons). Larger RVs might have 40 lb (10 gallons) or even bigger tanks.

• Good: You’ve got a clear number like “30 LB”.
• Mistake: Confusing the tare weight (empty weight) with the gross weight (full weight). The stamped capacity is what you need.

4. Check for Multiple Tanks: Many campers have more than one tank. If you have two tanks, they are often identical in size.

• Good: You’ve accounted for all tanks and their individual sizes.
• Mistake: Only checking one tank when there’s another one connected. This gives you an incomplete picture.

5. Look for Manufacturer Info: If the markings are illegible, look for a manufacturer’s label or data plate on the tank. This often contains more details.

• Good: A legible plate with model and serial numbers, from which you can often deduce capacity.
• Mistake: Giving up if the numbers are hard to read. There’s usually more info if you look hard.

6. Consult Your RV Manual: If tank markings are a no-go, grab your RV’s owner’s manual. It’s your best friend for specs.

• Good: The manual clearly states the propane tank size and number.
• Mistake: Assuming the manual is outdated. Most manuals are accurate for the original build.

7. Check Online Specs: If you have the RV’s make, model, and year, a quick online search for its specifications can often reveal the original propane tank setup.

• Good: Finding a manufacturer’s PDF spec sheet online.
• Mistake: Relying on random forum posts without verifying the source. Stick to official manufacturer sites.

8. Estimate Based on Appliances (if necessary): If all else fails, consider your appliances. A basic setup (stove, water heater) might be fine with smaller tanks, while a furnace and fridge point to larger capacity needs.

• Good: Using appliance needs as a confirmation, not the primary method.
• Mistake: Guessing your tank size purely on appliance needs without any physical evidence. This can lead to running out of fuel unexpectedly.

Common mistakes (and what happens if you ignore them)

Mistake	What it causes	Fix
Ignoring tank markings	Running out of propane unexpectedly, not knowing how much to refill.	Always check the stamped size on the tank itself.
Assuming both tanks are the same size	Underestimating your total propane capacity, leading to early refills.	Inspect and record the size of every tank you have.
Not checking the RV manual	Missing crucial information if tank markings are damaged or missing.	Keep your RV manual handy and refer to it for specifications.
Relying solely on tank weight	Misjudging fuel level; weight varies greatly between empty and full.	Use the stamped capacity (lbs or gallons) as the primary identifier.
Forgetting about secondary tanks	Not knowing your full propane reserve, potentially leaving you stranded.	Always account for all propane tanks connected to your system.
Not knowing the conversion (lbs to gal)	Difficulty communicating needs at a refill station or understanding usage.	Remember ~20 lbs = 5 gallons, ~30 lbs = 7.5 gallons, ~40 lbs = 10 gallons. (Exact conversion varies slightly)
Not checking for damage/leaks	Safety hazard; could lead to propane loss or dangerous situations.	Visually inspect tanks for rust, dents, or valve issues. If in doubt, get it checked by a pro.
Not verifying online specs	Getting incorrect information from unofficial sources, leading to bad assumptions.	Cross-reference online specs with your RV’s VIN or model number from the manufacturer.
Confusing propane tank size with BBQ tank size	Trying to use a smaller BBQ tank for a larger RV system, leading to insufficient fuel.	RV tanks are typically much larger than portable BBQ tanks. They are sized for extended use.

Decision rules (simple if/then)

• If you see “20 LB” stamped on the tank, then you have a common 5-gallon propane tank because that’s the standard conversion.
• If you see “30 LB” stamped on the tank, then you have a 7.5-gallon propane tank because that’s the typical capacity for that marking.
• If you can’t find any markings on the tank, then check your RV’s owner’s manual because it should list the original equipment.
• If your RV has a furnace and a propane fridge, then you likely have at least two 30 lb tanks or larger because these appliances draw a lot of fuel.
• If you only use propane for cooking and a small water heater, then a single 20 lb tank might be sufficient for shorter trips because those appliances are less demanding.
• If you have a very large motorhome with multiple slides and a residential fridge, then you might have 40 lb tanks or even a larger built-in tank because of the high energy demands.
• If you have multiple tanks and they look different, then check each one individually because they might be different sizes.
• If you’re unsure about the conversion from pounds to gallons, then look it up online or ask at the refill station because knowing this helps with planning.
• If a tank looks significantly dented or rusted, then get it inspected by a professional before refilling because safety is paramount.
• If you’re buying a used RV, then verify the propane tank sizes yourself, don’t just trust the seller’s word because things can change.

FAQ

Q: How do I know if my propane tank is full?

A: The best way is to use a propane gauge, which can be electronic or a simple dipstick type. You can also weigh the tank; a full 20 lb tank weighs about 38 lbs (empty tank + 20 lbs propane).

Q: What’s the difference between a 20 lb and a 30 lb propane tank?

A: A 20 lb tank holds roughly 5 gallons of propane, while a 30 lb tank holds about 7.5 gallons. They are physically different in size and weight.

Q: Can I mix different sized propane tanks on my RV?

A: Yes, you can usually mix different sizes, but it’s generally best practice to have identical tanks for simplicity in refilling and regulator setup. Check your RV’s manual for specific recommendations.

Q: How long will a 20 lb propane tank last?

A: It depends heavily on usage. For basic cooking and heating water, it might last several days. Running a furnace constantly will drain it much faster.

Q: Where can I get my propane tank refilled?

A: Many gas stations, hardware stores, and dedicated propane dealers offer refills. RV parks and campgrounds sometimes have refill services too.

Q: Is it safe to transport a propane tank horizontally?

A: Propane tanks are designed to be transported vertically. While some small portable tanks have specific horizontal adapters, larger RV tanks should always be secured upright.

Q: What does “DOT” mean on a propane tank?

A: DOT stands for the Department of Transportation. It indicates that the tank has met specific safety standards set by the US DOT for transportation.

Q: My tank has a lot of rust. Is it still safe?

A: Surface rust might be cosmetic, but deep pitting or rust around the valve or collar is a safety concern. If in doubt, have it inspected by a qualified propane professional.

What this page does NOT cover (and where to go next)

• Detailed propane consumption rates for specific appliances. (Next: Research appliance energy usage).
• How to safely connect and disconnect propane tanks. (Next: Consult your RV manual or a professional).
• Propane leak detection methods and emergency procedures. (Next: Learn about propane safety and leak detectors).
• The process of refilling a propane tank. (Next: Find a local refill station and ask about their procedures).
• Regulations for transporting propane tanks. (Next: Check DOT guidelines or local fire department rules).