Temperature Converter - Complete Guide

Temperature converter transforms between Celsius (°C), Fahrenheit (°F), and Kelvin (K). Unlike other unit conversions, temperature uses different zero points, requiring both multiplication and addition. Essential for cooking, weather, science, and international communication.

How It Works

Temperature conversions require formulas, not simple ratios. Celsius to Fahrenheit: multiply by 9/5 (or 1.8), then add 32. Fahrenheit to Celsius: subtract 32, then multiply by 5/9. Kelvin is Celsius + 273.15 (absolute zero offset).

Technical Details

Celsius: 0° = water freezing, 100° = water boiling (at 1 atm). Fahrenheit: 32° = freezing, 212° = boiling. Kelvin: 0 = absolute zero (-273.15°C), no negative values. The scales intersect at -40° (same in both C and F). Rankine is Fahrenheit's absolute scale (rarely used).

Common Use Cases

1. Cooking & Baking: Convert oven temperatures between US (°F) and European (°C) recipes.
   • Example: 350°F = 177°C
2. Weather & Travel: Understand weather forecasts in unfamiliar temperature scales.
3. Science & Engineering: Convert lab temperatures, use Kelvin for thermodynamic calculations.
4. Medical: Convert body temperature readings between systems.
   • Example: 98.6°F = 37°C normal body temp

Code Examples

JavaScript Temperature Converter

function celsiusToFahrenheit(c) {
  return (c * 9/5) + 32;
}

function fahrenheitToCelsius(f) {
  return (f - 32) * 5/9;
}

function celsiusToKelvin(c) {
  return c + 273.15;
}

function kelvinToCelsius(k) {
  return k - 273.15;
}

// Convert any to any via Celsius
function convertTemp(value, from, to) {
  // First convert to Celsius
  let celsius;
  switch(from) {
    case 'C': celsius = value; break;
    case 'F': celsius = (value - 32) * 5/9; break;
    case 'K': celsius = value - 273.15; break;
  }
  // Then convert from Celsius to target
  switch(to) {
    case 'C': return celsius;
    case 'F': return (celsius * 9/5) + 32;
    case 'K': return celsius + 273.15;
  }
}

// Examples
convertTemp(100, 'C', 'F');  // 212 (boiling point)
convertTemp(0, 'C', 'K');    // 273.15
convertTemp(98.6, 'F', 'C'); // 37 (body temp)

Temperature conversion requires formulas with offsets, not just multipliers. Convert through Celsius as intermediate.

Tips & Best Practices

• Quick C to F estimate: double and add 30
• Quick F to C estimate: subtract 30 and halve
• -40 is the same in both C and F
• Room temperature: ~20-22°C or ~68-72°F
• Oven temps: 180°C ≈ 350°F, 200°C ≈ 400°F

Common Mistakes to Avoid

• Forgetting the +32 or -32 offset
• Using wrong order of operations
• Confusing Kelvin offset (273.15)
• Assuming linear scaling without offset

When to Use This Tool

Use temperature converter for cooking, weather, scientific work, medical readings, and any cross-cultural communication involving temperatures.

Frequently Asked Questions

What is the formula for Celsius to Fahrenheit?

°F = (°C × 9/5) + 32, or equivalently °F = (°C × 1.8) + 32. Example: 20°C = (20 × 1.8) + 32 = 68°F.

When are Celsius and Fahrenheit equal?

At -40°. This is the only point where both scales show the same number: -40°C = -40°F.

What is Kelvin used for?

Kelvin is used in science because it starts at absolute zero (no negative values). Temperature ratios only make sense in Kelvin. 0K = -273.15°C = -459.67°F.

What is normal body temperature?

37°C = 98.6°F. However, normal ranges from 36.1-37.2°C (97-99°F). Fever is typically above 38°C (100.4°F).

Get Started

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Last updated: June 27, 2026