Propane Weight Calculator (Gallons to Pounds)
Calculate the approximate weight of a given volume of liquid propane in pounds. This is useful for estimating fill levels and transport weights.
Enter Propane Volume
Understanding Propane Weight
Liquid propane's weight is relatively consistent under typical conditions, though its volume can change slightly with temperature. Knowing the weight per gallon allows for easy conversion between volume (how propane is often sold or measured in tanks) and weight (useful for capacity ratings and handling).
The Formula
The approximate weight is calculated as:
Weight (lbs) = Gallons × 4.2 lbs/gallon
Note: The commonly accepted average weight is ~4.2 pounds per US gallon at 60°F (15.6°C). Some sources use 4.24 lbs/gallon for higher precision.
Why is this Conversion Useful?
- Estimating Tank Contents: If you know the gallon capacity of your tank and its current percentage, you can estimate the weight of the propane inside.
- Filling Stations: Propane is often dispensed by the gallon, but tanks (especially smaller ones like grill tanks) are rated by their propane weight capacity (e.g., 20 lb tank).
- Transportation & Handling: Knowing the weight helps ensure safe lifting and transport, especially for portable cylinders.
- Appliance Consumption: Some appliance usage is measured in pounds per hour, while fuel might be purchased in gallons.
Examples with Step-by-Step Solutions
Click on each example to see the calculation:
Example 1: Standard Grill Tank (Approx. Fill)
Given:
- Volume = 4.7 Gallons (typical fill for a "20 lb" tank)
Steps:
- Use Formula: Weight (lbs) = Gallons × 4.2
- Calculate: 4.7 Gallons × 4.2 lbs/Gallon
Result: Weight ≈ 19.7 lbs
Example 2: Small Volume
Given:
- Volume = 1 Gallon
Steps:
- Use Formula: Weight (lbs) = Gallons × 4.2
- Calculate: 1 Gallon × 4.2 lbs/Gallon
Result: Weight = 4.2 lbs
Example 3: Medium Tank Volume
Given:
- Volume = 100 Gallons
Steps:
- Use Formula: Weight (lbs) = Gallons × 4.2
- Calculate: 100 Gallons × 4.2 lbs/Gallon
Result: Weight = 420 lbs
Example 4: Partial Gallon
Given:
- Volume = 0.5 Gallons
Steps:
- Use Formula: Weight (lbs) = Gallons × 4.2
- Calculate: 0.5 Gallons × 4.2 lbs/Gallon
Result: Weight = 2.1 lbs
Example 5: Large Residential Tank (Partial Fill)
Given:
- Volume = 350 Gallons
Steps:
- Use Formula: Weight (lbs) = Gallons × 4.2
- Calculate: 350 Gallons × 4.2 lbs/Gallon
Result: Weight = 1470 lbs
Frequently Asked Questions (FAQs)
Why use 4.2 lbs per gallon?
This is a widely accepted average weight for liquid propane at a standard temperature (60°F). The actual weight can vary slightly based on temperature and pressure, but 4.2 lbs/gallon is standard for most practical calculations. Some technical sources use 4.24 lbs/gallon.
Does temperature affect the weight?
Temperature primarily affects the *volume* of propane (it expands when warmer, contracts when cooler). The *mass* (and therefore weight) of a contained amount of propane doesn't change significantly with temperature, but the *density* (weight per unit volume) does. The 4.2 lbs/gallon figure assumes a standard temperature.
Is this the total weight of the tank?
No. This calculator only determines the weight of the *propane liquid* itself. To find the total weight of a full or partially full tank, you need to add the weight of the propane (calculated here) to the empty weight of the tank (often called "Tare Weight" or "T.W.", usually stamped on the tank collar).
How many gallons are in a standard "20 lb" grill tank?
A "20 lb" tank is designed to hold 20 pounds of propane by weight. Using the conversion (20 lbs / 4.2 lbs/gallon), this equates to approximately 4.76 gallons. Due to safety regulations (requiring an expansion space), tanks are typically filled to about 80% of their liquid capacity, which is why a 20 lb tank usually receives around 4.7 gallons.
Can I use this for other gases like butane or natural gas?
No. This conversion factor (4.2 lbs/gallon) is specific to liquid propane. Other gases have different densities and weights per gallon.
