Calculate propane delivery cost, estimate gallons needed to raise a tank’s fill level, or find how much propane fits within a total budget after fees and tax.
Propane Cost Formula
For a known delivery quantity, multiply gallons by the price per gallon, apply sales tax to the propane subtotal, and add fixed delivery fees:
C = G * P * (1 + T) + F
When estimating a tank fill from one gauge percentage to another:
G = V * (Pt - Ps) / 100
To find the gallons available within a total budget:
G = (B - F) / [P * (1 + T)]
Variables:
- C is the estimated propane purchase cost
- G is the number of gallons delivered
- P is the propane price per gallon
- T is the sales-tax rate written as a decimal
- F is the total of delivery and other fixed fees
- V is the tank’s nominal capacity in gallons
- Ps and Pt are the starting and target gauge percentages
- B is the maximum total budget
The tank-fill method estimates the change in liquid volume from the gauge percentages. Actual delivered gallons can differ because tank gauges are approximate, nominal tank capacity may not equal usable capacity, and safe fill limits depend on the tank and supplier.
Estimated Gallons for a Tank Fill
The table shows the gallons needed to raise several nominal tank sizes from 20 percent to 80 percent, plus the propane subtotal at $2.75 per gallon before tax and fees.
| Nominal tank size | Fill increase | Estimated gallons | Propane subtotal |
|---|---|---|---|
| 120 gallons | 20% to 80% | 72 gallons | $198.00 |
| 250 gallons | 20% to 80% | 150 gallons | $412.50 |
| 325 gallons | 20% to 80% | 195 gallons | $536.25 |
| 500 gallons | 20% to 80% | 300 gallons | $825.00 |
| 1,000 gallons | 20% to 80% | 600 gallons | $1,650.00 |
These are mathematical estimates, not filling instructions. The supplier determines the permitted target level and the quantity placed in the tank.
Example Problems
Example 1: Find the cost of a propane delivery.
A delivery contains 150 gallons at $2.75 per gallon. Sales tax is 3 percent, the delivery fee is $25, and other fixed fees are $5. The propane subtotal is $412.50, tax is $12.38, and fixed fees total $30:
C = $412.50 + $12.38 + $30 = $454.88.
Example 2: Find gallons available within a budget.
A customer has $500, propane costs $2.50 per gallon, tax is 4 percent, and fixed fees are $20. The affordable quantity is:
G = ($500 - $20) / [$2.50 * 1.04] = 184.62 gallons.
Frequently Asked Questions
How do I estimate the gallons needed to fill a propane tank?
Subtract the starting gauge percentage from the target percentage and multiply that difference by the tank’s nominal gallon capacity. Treat the result as an estimate and confirm the actual delivery and safe fill level with the supplier.
Why is the effective cost per gallon higher than the quoted price?
The quoted price may cover only the propane. Delivery charges, minimum-delivery fees, hazmat or fuel surcharges, tank rental, and tax can raise the total amount paid per delivered gallon.
How can I estimate how long a delivery will last?
Divide delivered gallons by average gallons used per day. Use a recent seasonal average because propane consumption can change sharply with outdoor temperature, thermostat settings, appliances, and household occupancy.
