WIN-J · TEMPERATURE LAB
Water mixing temperature calculator
Find the mixed temperature of hot and cold water, or the amounts needed for a target temperature and total quantity. Review the mass-based heat-balance approximation and volume assumptions, then export the results.
Calculation results
This approximation assumes equal, constant specific heat and no heat loss. Containers, evaporation, ice, steam and temperature-dependent heat capacity are omitted; measure and adjust the actual mixture.
Compare the relationship between the inputs and calculated values.
How to use
- Choose whether to calculate temperature from water amounts or amounts for a target temperature.
- Select a temperature unit and enter cold and hot water temperatures. The hot temperature must be at least the cold temperature.
- Use one selected amount unit throughout. In mixing mode enter both amounts; in target mode enter the target temperature and total amount.
- Review the mixed temperature, required amounts and shares, then copy the results or download CSV.
- Measure and adjust the actual mixture. The calculation does not include heat absorbed by the container or temperature-dependent water properties.
Worked example
Mixing 200 g at 80°C with 300 g at 20°C gives an ideal temperature of (200×80+300×20)/500=44°C. To make 1000 g at 40°C from those temperatures, use about 333.33 g of hot water and 666.67 g of cold water.
Methods and limits
Assumes the same liquid water has equal, constant specific heat and loses no heat externally. Mixed temperature is (hot mass×hot temperature+cold mass×cold temperature)/total mass. For a target split, hot mass is total mass×(target−cold)/(hot−cold). All temperatures must be 0–100°C (32–212°F), and the target must lie between the input temperatures. A target at either endpoint allows zero of the other water. Equal input temperatures permit mixing calculations but do not determine a unique target split. Amounts must be non-negative; after unit conversion, the total must be above 0 and at most 1,000,000,000 g. g and kg are mass units; mL and L approximate 1 mL of water as 1 g. Temperature-dependent density and heat capacity, container heat capacity, evaporation, phase changes of ice/steam and other liquids are excluded. Changing units does not convert entered numbers.
Frequently asked questions
Are mL and L as exact as weighed amounts?
Volume input approximates 1 mL of water as 1 g. Actual density varies with temperature, so distinguish this from directly weighed g or kg. Both amounts must use the same selected unit.
Why might the actual mixture be warmer or cooler?
The calculation uses ideal heat balance with constant specific heat and no heat loss. Real containers, surrounding air, evaporation, measurement position and timing affect the result. Measure the actual mixture and adjust it.
What if the temperatures are equal or the target is outside them?
Equal temperatures can still be mixed in specified amounts. They do not determine a unique split for a target temperature. A target outside the two temperatures is unreachable using those two waters alone; at an endpoint the amount of the other water is zero.
Can I use ice, steam, milk or dough?
This tool models the same liquid water only. Ice and steam require phase-change heat, while milk and dough have different heat capacities. Do not apply this water-only model to those materials unchanged.
What happens to inputs when units change?
Numbers remain unchanged and are reinterpreted in the new units. They are not automatically converted, so enter all temperatures and amounts consistently. The default example uses Celsius and grams.