Boiling Point & Fuel Calculator

How to use the boiling point calculator

1. Enter your altitude in metres.
2. Set how many litres you boil per day (drinking water, meals, hot drinks) and the number of days.
3. Enter the starting water temperature – stream water is often 5–10 °C.
4. Choose the wind at the stove and whether you use a pot with lid.

How it is calculated

First the air pressure at your altitude is calculated with the standard barometric formula. The boiling point then follows from the Antoine equation for water, which links vapour pressure and temperature. Roughly, the boiling point drops by about 1 °C for every 300 m of altitude.

For safe drinking water the calculator follows the CDC/WHO recommendation: bring water to a rolling boil for 1 minute, or 3 minutes above 2,000 m, because water boils at a lower temperature there.

Fuel is estimated from the energy needed to heat each litre (4.186 kJ per litre and degree) divided by stove efficiency: 55 % in calm conditions or with a windscreen, 40 % in a breeze, 25 % in wind, and 20 % less without a lid. The model assumes a 2.6 kW canister stove at full flame (about 4–5 minutes to boil a litre in calm air), gas with 46 kJ per gram and the rolling boil held at about 1.2 kW. For a campfire it assumes dry wood with 15 MJ/kg and only about 6 % efficiency.

Practical tips

• Use a windscreen and a lid: at sea level the model needs about 17 g of gas per litre in calm air but around 35 g in strong wind.
• Boiling kills bacteria, viruses and parasites but does not remove chemicals, heavy metals or salt.
• Food cooks slower at altitude – pasta and rice need more time and more fuel.
• Gas canisters lose power below about 0 °C; keep them warm in your jacket.