Gas Bottle Calculator
Estimate how much propane or butane remains in your gas bottle using its tare weight and current weight. Enter weights in kilograms or pounds and ounces, then compare the remaining gas with the bottle’s rated gas capacity.
The litre figure is an approximate liquid LPG equivalent. This tool is for checking remaining contents and planning supplies; it must not be used to decide how much to refill.
How to check the gas remaining
- Select propane, butane or unknown LPG blend to match the bottle’s contents.
- Enter the rated gas capacity printed on the bottle or supplier’s label. This is the gas charge in kg, rather than the weight of the full bottle.
- Enter the bottle’s own empty (tare) weight and its current total weight. Use the unit selector beside each field to choose kg or lb/oz.
- Read the estimated gas weight, percentage remaining and liquid-equivalent litres. You can save a bottle’s details in this browser for next time.
Worked example: a 6 kg propane bottle
Suppose a bottle has a 6 kg rated gas capacity, a tare weight of 7 kg and a current total weight of 10 kg. The estimated gas remaining is 10 − 7 = 3 kg, or 50% of its rated gas charge.
Using this calculator’s approximate propane density of 0.51 kg per litre, 3 kg is about 5.9 litres of liquid LPG. This is an estimate of the liquid inside the bottle, not the volume of gas released at atmospheric pressure.
What do litres and “deficit” mean?
Remaining gas mass is calculated by subtracting tare weight from current total weight. Litres are estimated from that mass and an assumed liquid density. Temperature and the propane/butane mixture affect density, so the litre result is less certain than the weight calculation.
“Deficit” is the difference from the bottle’s rated gas charge, expressed as an approximate liquid equivalent. It is not a safe refill quantity or a measurement of expansion headroom. A kg gas rating does not establish the bottle’s internal water capacity. Do not refill exchange cylinders yourself or use these estimates to set a filling limit.
Getting a useful estimate
Use the tare weight for this particular bottle: two bottles with the same gas rating can have different empty weights. A bottle labelled 6 kg or 13 kg specifies its gas charge, not its total weight. Do not disturb a connected cylinder merely to weigh it; follow the supplier’s safe handling instructions. Added accessories or an inaccurate scale can distort the result. The percentage describes the remaining rated gas charge; estimating how many hours it will last also requires your appliances’ consumption rates.
Planning your time off-grid? Try the leisure battery runtime calculator for lights, TVs, phone chargers and other appliances.
Gas bottle guides: weight, runtime and fuel choice
Read empty and full gas bottle weight explained for tare markings and pounds-and-ounces conversion. To turn remaining gas into hours or days, use our gas bottle runtime guide. For seasonal touring, compare propane and butane for caravans and camping.
Gas bottle calculator FAQs
Where do I find the tare weight?
The empty-cylinder or tare weight is normally stamped or printed on the bottle or collar. Use the marking for your actual bottle rather than assuming all bottles of the same gas size weigh the same.
Why can two 13 kg bottles weigh different amounts when full?
The quoted 13 kg is the gas charge, not the complete bottle weight. Steel cylinder weights vary, so two bottles carrying the same amount of LPG can have different total weights.
Does 50% gas remaining mean 50% of the original runtime?
Not necessarily. Runtime depends on which appliances are being used and their gas consumption, so percentage remaining is best treated as a fuel-level estimate.