Temperature Converter

Temperature Unit Conversion — Celsius, Fahrenheit, Kelvin, and Rankine

Temperature is one of the most frequently converted quantities in daily life — weather forecasts, cooking recipes, scientific papers, and medical readings all use different scales depending on country and context. The Toolsiro Temperature Converter converts between four temperature scales (Celsius, Fahrenheit, Kelvin, and Rankine) simultaneously, with a visual thermometer display and clickable reference points for common temperatures.

The Four Temperature Scales

Celsius (°C) — the most widely used scale globally. Defined so that water freezes at 0°C and boils at 100°C at standard atmospheric pressure. Used in weather forecasts, cooking, and scientific contexts in most of the world. Named after Swedish astronomer Anders Celsius (1701–1744).

Fahrenheit (°F) — used primarily in the United States, its territories, and a few Caribbean nations. Water freezes at 32°F and boils at 212°F. Human body temperature is 98.6°F. The scale was proposed by German physicist Daniel Gabriel Fahrenheit in 1724. To convert: °F = (°C × 9/5) + 32.

Kelvin (K) — the SI unit of temperature, used in science and engineering. Unlike Celsius and Fahrenheit, Kelvin is an absolute scale — 0 K is absolute zero, the theoretical lowest possible temperature (−273.15°C), where molecular motion essentially stops. There are no negative Kelvin values. To convert: K = °C + 273.15. Used in physics, chemistry, astrophysics, and engineering calculations.

Rankine (°R) — an absolute temperature scale like Kelvin, but based on Fahrenheit degrees. 0°R is absolute zero; water freezes at 491.67°R and boils at 671.67°R. Used in some US engineering applications, particularly in thermodynamics. To convert: °R = (°C + 273.15) × 9/5.

Conversion Formulas

• Celsius → Fahrenheit: °F = (°C × 9/5) + 32
• Fahrenheit → Celsius: °C = (°F − 32) × 5/9
• Celsius → Kelvin: K = °C + 273.15
• Kelvin → Celsius: °C = K − 273.15
• Celsius → Rankine: °R = (°C + 273.15) × 9/5

Important Reference Temperatures

• Absolute zero: −273.15°C / −459.67°F / 0 K — the coldest possible temperature
• Water freezing: 0°C / 32°F / 273.15 K
• Room temperature: ~20–22°C / 68–72°F / 293–295 K
• Human body temperature: 37°C / 98.6°F / 310.15 K
• Water boiling (sea level): 100°C / 212°F / 373.15 K
• Oven temperatures: 180°C (350°F) for baking, 200°C (400°F) for roasting
• Surface of the Sun: ~5,500°C / ~9,900°F / ~5,773 K

Practical Temperature Guide for Everyday Life

• Weather: Below 0°C (32°F) = freezing; 15–20°C (59–68°F) = mild; 30°C+ (86°F+) = hot
• Cooking — meat: Chicken safe at 74°C (165°F); beef medium at 63°C (145°F)
• Cooking — baking: Most bread baked at 190–220°C (375–425°F)
• Refrigerator: 1–4°C (34–40°F); freezer: −18°C (0°F)
• Fever: Above 38°C (100.4°F) in adults

Related Unit Converters

For length conversions use the Length Converter. For weight use the Weight Converter.