What is the freezing and boiling point of water on the Fahrenheit scale?

On the Fahrenheit scale, pure water freezes at 32°F and boils at 212°F at normal atmospheric pressure (sea level, 1atm).

When we talk about the freezing and boiling points of water, we mean the temperatures at which water changes state under standard pressure. On the Fahrenheit scale, which is widely used in the United States, the lower fixed point is set at 32°F (freezing/melting of water) and the upper fixed point is 212°F (boiling/condensation of water). The gap between these points is 180 equal divisions, which is why one Fahrenheit degree is smaller than one Celsius degree.

These values are valid at 1 atmosphere of pressure (approximately sea level). If the air pressure changes, the boiling point shifts. For example, at high altitudes where pressure is lower, water may boil well below 212°F; at higher pressure (like in a pressure cooker), it boils above 212°F. The freezing point is far less affected by normal pressure changes but can be lowered by dissolved substances (salt, sugar), which is how de-icing salt works on winter roads.

Many learners wonder why 0°F is not used for water’s freezing point. Historically, 0°F was chosen near the coldest mixture Daniel Fahrenheit could make (a brine of ice, water, and salt). He then set the temperature of a healthy human body near 96°F (later refined to 98.6°F). This is why water’s freezing point is 32°F rather than 0°F, and boiling is 212°F, making exactly 180 degrees between them. To convert between scales, use these helpful formulas:

• °F = (°C × 9/5) + 32
• °C = (°F − 32) × 5/9