Fahrenheit to Celsius Converter Guide: Temperature Conversion Made Simple

°C = (°F − 32) × 5/9

Or equivalently: °C = (°F − 32) ÷ 1.8

Examples: • 98.6°F (body temperature): (98.6 − 32) × 5/9 = 66.6 × 0.556 = 37°C • 72°F (comfortable room): (72 − 32) × 5/9 = 40 × 0.556 = 22.2°C • 350°F (oven): (350 − 32) × 5/9 = 318 × 0.556 = 176.7°C • 0°F: (0 − 32) × 5/9 = −32 × 0.556 = −17.8°C

• °C = (°F − 32) × 5/9 — the exact formula
• Subtract 32 first, then multiply by 5/9
• Multiplying by 5/9 is the same as dividing by 1.8
• Key check: 32°F = 0°C (freezing point of water)

°F = (°C × 9/5) + 32

Or equivalently: °F = (°C × 1.8) + 32

Examples: • 100°C (boiling point): (100 × 1.8) + 32 = 180 + 32 = 212°F • 37°C (body temperature): (37 × 1.8) + 32 = 66.6 + 32 = 98.6°F • 20°C (room temperature): (20 × 1.8) + 32 = 36 + 32 = 68°F • −40°C: (−40 × 1.8) + 32 = −72 + 32 = −40°F (the point where both scales are equal)

• °F = (°C × 9/5) + 32 — the exact formula
• Multiply by 1.8 (or 9/5) first, then add 32
• Key check: 100°C = 212°F (boiling point of water)
• −40° is the unique point where Fahrenheit and Celsius are equal

For quick mental estimates:

F to C shortcut: subtract 30, divide by 2 • 70°F: (70 − 30) / 2 = 20°C (exact: 21.1°C — close enough for weather) • 100°F: (100 − 30) / 2 = 35°C (exact: 37.8°C)

C to F shortcut: double, add 30 • 25°C: (25 × 2) + 30 = 80°F (exact: 77°F) • 15°C: (15 × 2) + 30 = 60°F (exact: 59°F)

These shortcuts are accurate within 2–3 degrees for typical weather temperatures. Don't use them for medical, scientific, or cooking applications where precision matters.

• F→C shortcut: (°F − 30) ÷ 2 (accurate within 2–3°C for weather)
• C→F shortcut: (°C × 2) + 30 (accurate within 2–3°F for weather)
• Useful for quick weather understanding when traveling internationally
• Not suitable for cooking or medical use — use exact formula

Memorizing key reference temperatures allows instant frame-of-reference:

Water: • Freezing: 32°F = 0°C • Boiling: 212°F = 100°C (at sea level)

Human body: • Normal: 98.6°F = 37°C • Low-grade fever: 100°F = 37.8°C • High fever: 103°F = 39.4°C

Weather: • Very cold: 14°F = −10°C | Freezing: 32°F = 0°C • Mild: 59°F = 15°C | Warm: 77°F = 25°C • Hot: 95°F = 35°C | Extreme: 104°F = 40°C

Cooking: • Refrigerator: 35–38°F = 2–3°C | Freezer: 0°F = −18°C • Bread baking: 375°F = 190°C | Roasting: 425°F = 218°C

• Freezing: 32°F = 0°C | Boiling: 212°F = 100°C
• Normal body temp: 98.6°F = 37°C
• Room temperature: 68–72°F = 20–22°C
• −40°F = −40°C (the scale equivalence point)

Kelvin is the SI base unit of temperature, used in physics and chemistry. Unlike Fahrenheit and Celsius, Kelvin has no negative values — zero Kelvin (0 K) is absolute zero, the coldest possible temperature.

Kelvin to Celsius: °C = K − 273.15 Celsius to Kelvin: K = °C + 273.15

Key Kelvin values: • Absolute zero: 0 K = −273.15°C = −459.67°F • Freezing water: 273.15 K = 0°C = 32°F • Boiling water: 373.15 K = 100°C = 212°F • Body temperature: 310.15 K = 37°C = 98.6°F • Room temperature: ~293 K = 20°C = 68°F

Kelvin is used in thermodynamics, astrophysics, and materials science where negative temperatures are physically meaningless.

• K = °C + 273.15 (or approximately °C + 273)
• 0 K = absolute zero — the coldest possible temperature
• No negative Kelvin temperatures exist in classical physics
• Kelvin is the SI base temperature unit used in all scientific work

Practical applications where conversion matters:

Travel: European weather forecasts use Celsius. 25°C is a warm summer day; 10°C is cool sweater weather; 0°C means frost and ice.

Cooking: most international recipes use Celsius. Common conversions: 180°C = 356°F (moderate oven); 200°C = 392°F (hot oven); 220°C = 428°F (very hot oven).

Medicine: fevers are measured in Celsius in most countries. Fever is ≥ 38°C (100.4°F). Rectal temperature is ~0.5°C higher than oral; axillary (armpit) ~0.5°C lower.

Refrigeration: food safety temperatures: refrigerator ≤ 4°C (40°F); freezer ≤ −18°C (0°F); hot holding ≥ 60°C (140°F).