Propane Usage Calculator
Turn your propane gauge reading into days: how many gallons a day your house is using this month, when to order a refill before you hit the 30% mark, when the tank runs dry, and what the month costs. Built on supplier usage figures by home size, scaled for mild, typical, and cold-snap weather.
Your tank gauge tells you a percentage. This turns it into days: how much propane the house is burning this month, when to call for a refill so you're not paying an emergency fee, and what the month will cost.
Your tank
It's stamped on the tank's data plate. The gauge reads percent of this size, and tanks only fill to 80%, so a full 500-gallon tank reads 80 and holds 400 gallons.
What the gauge reads now
The dial under the tank's lid, 5 to 95. It reads percent of the tank's rated size, so 60 on a 500-gallon tank is 300 gallons, and 80 is a full fill.
Your house and the weather
The part of the house the propane furnace heats. A typical home is 1,500–2,500 sq ft.
What's the weather doing this month?
What else runs on propane?
What you pay per gallon
From your last delivery ticket. The national residential average was about $2.67 at the end of last season; contract and prebuy prices differ.
Order a refill in about
35 days
300 gallons (60% of 500) at 4.3 a day; order around Nov 5.
Why 30%, and why the tank only fills to 80%
Suppliers ask you to order at 30% because a routine delivery takes up to seven business days, and a cold week can burn the last 20% faster than the truck arrives; below 30% you're into expedited fees, and an empty tank means a pressure test and a relight visit. The tank never fills past 80% because propane expands as it warms, so a "full" 500-gallon tank is 400 gallons and every gauge reading is a percentage of the tank, not of what you paid for.
What moves the number
The furnace is almost all of it: a cold snap burns about one and a half times what a typical winter month does, a mild month barely half, so the same tank can last six weeks or three months depending on the calendar. The water heater is a steady half to three-quarters of a gallon a day whatever the weather, and cooking and drying together are a fraction of that. If your usage runs well above this, the usual reasons are an old furnace, a thermostat held high, or heating rooms nobody uses; if the gauge drops faster than the math, have the supplier check for a leak.
Heating use is a supplier's winter-month figure for your home size, scaled by heating degree days for the weather you pick; other appliances use published monthly figures. Tanks fill to 80% and suppliers ask for orders at 30%. Actual burn depends on the furnace, insulation and thermostat. Price defaults to the last EIA national average. 2026 figures.
💡About this calculator▼
A propane gauge tells you a percentage and leaves the rest to you. What you actually want to know is a date: when to call for a delivery so the truck arrives on the regular schedule, not at an emergency rate, and not after the furnace has already gone out.
The furnace is nearly the whole bill. Suppliers publish how much propane an ordinary house burns in a winter month by its size, and that number moves with the weather more than anything else: a cold snap burns about half again as much as a typical winter month, a mild stretch barely half. The water heater adds a steady half to three-quarters of a gallon a day; the range and dryer together add a fraction of that.
Two rules the calculator builds in. Tanks only fill to 80 percent, so a full 500-gallon tank holds 400 gallons and every gauge reading is a percentage of the tank, not of what you can burn. And suppliers ask for an order at 30 percent, because a routine delivery takes up to a week. So the headline here is not "days until empty," which is the number that gets people in trouble, but days until the reorder mark.
Start with what's in the tank. A propane tank's gauge reads percent of the tank's rated size, and a tank is only ever filled to 80 percent to leave room for the gas to expand. So a 500-gallon tank at 60 percent holds 300 gallons, and "full" is 400.
Then how fast it's leaving. Propane suppliers publish what an ordinary house burns in a winter month: about 60 to 80 gallons for 1,000 square feet, 80 to 100 for 1,500, and 100 to 120 for 2,000. The calculator draws a line through those figures for your square footage and divides by 30 for a daily rate. That figure is for a typical winter month, so the weather card scales it by heating degree days, the measure utilities use: a month averaging 45°F needs about 57 percent of the heat of one averaging 30°F, and a cold snap averaging 15°F needs about 143 percent.
Add the other appliances. A propane water heater uses about 15 to 25 gallons a month whatever the weather; a range about 3 to 5; a dryer 1.5 to 2. The calculator adds the midpoints for whichever you have.
Turn gallons into dates. Gallons in the tank divided by gallons a day is the days until empty. Suppliers ask you to order at 30 percent, so the days until the reorder mark is the gallons above 30 percent divided by the daily rate, and that is the headline. Multiply the daily rate by 30 and by your price per gallon for the monthly cost.
📐How it's calculated▼
Gallons in the tank = tank size × gauge reading. A 500-gallon tank reading 80 percent holds 400 gallons, which is full; at 60 percent, 300.
Typical-month heating gallons = 70 + 0.04 × (square feet − 1,000). That line runs through the supplier's table: 1,000 sq ft gives 70, 1,500 gives 90, 2,000 gives 110. For a 2,000-square-foot house that is 110 gallons a month, or 3.7 gallons a day.
Weather factor = (65 − average temperature) ÷ (65 − 30). A typical winter month averaging 30°F is 1.0. A cold snap averaging 15°F is 50 ÷ 35 = 1.43, so the same house burns 5.2 gallons a day. A mild month averaging 45°F is 20 ÷ 35 = 0.57, or 2.1 gallons a day.
Other appliances. A water heater adds 20 gallons a month, about 0.7 a day; range and dryer together add about 5.75 a month.
Worked example. A 2,000-square-foot house with a propane furnace and water heater, 500-gallon tank at 80 percent, typical winter, $2.67 a gallon: 3.7 + 0.7 = 4.3 gallons a day. The 400 gallons last 93 days, and the 250 gallons above the 30 percent mark last 58 days, so that is when to order. The month costs 4.3 × 30 × 2.67 = $344. The supplier's own statement that a full 500-gallon tank lasts two to four months in winter lands right in the middle of that.
📎Sources:U.S. Energy Information Administration — Heating Oil and Propane Update (residential propane prices),U.S. Energy Information Administration — Degree Days (heating degree day definition),AmeriGas — Propane Tank Sizes (capacity at the 80% fill),Kauffman Gas — How Much Propane Does Your Home Really Need (monthly usage by home size and appliance)
🔍Finding your inputs▼
Tank size: On the tank's data plate, or ask your supplier. Residential tanks are 120, 250, 500, or 1,000 gallons; 500 is the common whole-house size. Remember the tank holds 80 percent of its rated size when full.
What the gauge reads now: Lift the lid on top of the tank; the dial runs from 5 to 95 and reads percent of the tank. Read it on the same day you use the calculator, since a cold day can move it a few points.
Heated square footage: The floor area the propane furnace heats. Leave out an unheated basement or garage. This is the biggest lever in the calculator because heating is most of the bill.
What's the weather doing this month: Pick by the month's average temperature, not the coldest night. Around 45°F is a mild shoulder month, around 30°F a typical winter month in most of the propane belt, and around 15°F a genuine cold snap or a northern January. The card scales the heating figure by heating degree days.
What else runs on propane: Just the furnace, the furnace plus a water heater, or everything including the range and dryer. Fireplaces, generators, and pool heaters are not included; they burn one to three gallons an hour when running and would need their own hours.
What you pay per gallon: From your last delivery ticket. The national residential average was about $2.67 at the end of the 2025–26 season, but contract, prebuy, and will-call prices differ by a dollar or more.
⚠️Special situations▼
My gauge is at 30% but the weather is mild. Do I really need to order now?
Yes, order, but you can let the supplier schedule it on the regular route rather than expedite. The 30 percent rule exists because a routine delivery takes up to seven business days and a cold front can arrive faster than the truck. In a mild month a 500-gallon tank at 30 percent, 150 gallons, is three or four weeks of propane for a typical house, so there is no emergency, but the point of the rule is to order while there is no emergency. If your supplier offers automatic delivery, this is the moment to switch; they track your usage and degree days and fill before you get here.
The tank ran empty. Can I just get it filled and turn things back on?
Not on your own. When a propane system loses pressure, the supplier is required to perform a leak check before restoring service, and every appliance with a pilot or ignition has to be relit and checked. That is a service visit on top of the delivery, usually with a fee, and it can take a day or two to schedule in the middle of winter. It is also why suppliers push the 30 percent rule so hard: the cost of running out is not the gas, it is the visit and the cold house while you wait for it.
I have a propane fireplace and a generator too. Why aren't they included?
Because their usage depends entirely on hours you choose, and those hours swing from zero to a lot. A gas fireplace burns about a gallon every three hours, so an evening a day through winter is another 20 to 30 gallons a month, and a standby generator burns two to three gallons an hour, which in a multi-day outage can empty a 500-gallon tank by itself. If you use either regularly, add their gallons to the daily rate shown here: an hour a day of fireplace is about a third of a gallon, and the standby generator runtime calculator will give you the outage figure.
My usage is far higher than the calculator says
Work through the list in order. First the weather card: a month with a real cold snap belongs on the cold card even if the calendar says November. Then the furnace: an old 80 percent unit, or one that is oversized and short-cycling, burns noticeably more than the supplier averages assume. Then the thermostat and the heated area, since a house held at 72 with a heated basement is not the ordinary house the figures describe. If none of that explains it and the gauge is dropping faster than the math over a week or two, call the supplier for a leak check; a smell of gas near the tank or the regulator makes that call urgent.
❓Common questions▼
How long will a 500-gallon propane tank last in winter?
About two to four months for a typical house, which matches what suppliers say. A full 500-gallon tank holds 400 gallons. A 2,000-square-foot home with a propane furnace and water heater uses about 4.3 gallons a day in a typical winter month, so the tank lasts about 93 days, and you would order at the 30 percent mark after about 58 days. In a cold snap the same house burns closer to six gallons a day and the tank lasts about two months; in a mild month under three gallons a day and it lasts well over four.
How much propane does a house use per day?
Mostly it depends on the furnace and the weather. Supplier figures put an ordinary 1,000-square-foot house at 60 to 80 gallons in a winter month, 1,500 square feet at 80 to 100, and 2,000 at 100 to 120, which is roughly 2.3 to 3.7 gallons a day for heat alone. A water heater adds about 0.7 gallons a day, a range and dryer together about 0.2. A cold snap raises the heating figure by about half; a mild month cuts it nearly in half. So a typical propane home runs somewhere between three and six gallons a day in winter.
Why is my propane tank only filled to 80%?
Because propane is stored as a liquid that expands as it warms, and the tank needs room for that expansion. Suppliers fill to 80 percent by rule, so a 500-gallon tank holds 400 gallons when full, a 250 holds 200, a 120 holds 96, and a 1,000 holds 800. The gauge reads percent of the tank's rated size, which is why it shows about 80 right after a fill and why every reading has to be multiplied by the tank size, not the fill, to get gallons.
When should I order a propane refill?
When the gauge reads 30 percent, or at least a week before you expect to need it. That is the number the major suppliers use because a routine delivery takes up to seven business days, and a cold week can burn through the last 20 percent faster than the truck arrives. Below 30 percent you may be paying an expedited delivery fee; at empty, the supplier has to leak-test the system and relight every appliance before restoring service. The calculator's headline is the days until you reach that 30 percent mark so you can put the order date on the calendar.
How much does propane cost per month for heating?
Multiply your daily gallons by 30 and by your price per gallon. At the national average of about $2.67 a gallon, a 2,000-square-foot house with a furnace and water heater in a typical winter month uses about 4.3 gallons a day, about $344 a month. A cold snap pushes that toward $470; a mild month drops it near $225. Prices vary widely by supplier and contract, so enter the number from your last delivery ticket rather than the average.
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