Temperature conversion formulas (°C, °F, K)

Temperature conversion looks simple — until you realize that Celsius and Fahrenheit do not start at the same zero point, and Fahrenheit uses a different degree size. Kelvin, meanwhile, is tied to absolute zero and is used heavily in science. This section explains the exact formulas used by the calculator so you can understand what’s happening (and even do it by hand if you need to).

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

• 32 is where water freezes on the Fahrenheit scale.
• 9/5 (or 1.8) converts the degree “size” between the two scales. One Celsius degree is bigger.
• 273.15 is the offset between Celsius and Kelvin (because 0°C is 273.15 K).

Notice something important: converting between Celsius and Kelvin is just an offset. If you increase a temperature by 10°C, you also increase it by 10 K. That’s why scientists love Kelvin for formulas and why you’ll often see temperature differences written in Kelvin (even when the “starting point” is in Celsius).

Fahrenheit is the odd one out: it has a different zero point and a different degree size. That’s why converting between °F and the other two scales needs both a shift (±32) and a scale factor (×5/9 or ×9/5).

Examples you’ll actually use

Here are the most common conversions people look up — weather, cooking, and “is this a fever?” checks. Use these as quick mental anchors, then let the calculator do the exact math when you want precision.

• 0°C ≈ 32°F (freezing)
• 10°C ≈ 50°F (cool hoodie weather)
• 20°C ≈ 68°F (comfortable)
• 30°C ≈ 86°F (hot)

• 180°C ≈ 356°F (common baking temperature)
• 200°C ≈ 392°F (hotter baking / roasting)
• 220°C ≈ 428°F (high-heat roasting)

• 37°C ≈ 98.6°F (average)
• 38°C ≈ 100.4°F (often considered fever threshold)

One more shortcut: Kelvin is Celsius plus 273.15. So 20°C is 293.15 K. If you’re doing physics homework, this simple shift saves time (and reduces mistakes).

How this Temperature Converter calculates results

This calculator follows a straightforward “convert-to-base, then convert-to-target” strategy to keep results consistent and easy to validate. That approach matters because there are multiple paths you can take when converting between three units, and tiny rounding choices can introduce small differences. Here’s the exact method used:

The tool first checks that you entered a valid number (including decimals and negative values). Negative temperatures are totally normal in Celsius and Fahrenheit (hello, winter). Kelvin is different: Kelvin values must be greater than or equal to 0. If you enter a negative Kelvin value, the tool flags it as invalid.

Internally, the converter first translates your “from” value into Celsius. Why Celsius? Because it’s the simplest intermediate for this set of units: Kelvin is a direct offset from Celsius, and Fahrenheit-to-Celsius is the standard conversion most people learn first.

• If you start with °C, the base value is the same number.
• If you start with °F, it applies (°F − 32) × 5/9.
• If you start with K, it applies K − 273.15.

Once the number is in Celsius, the tool converts to the “to” unit using the appropriate formula. For example, Celsius → Fahrenheit applies (°C × 9/5) + 32 and Celsius → Kelvin applies °C + 273.15.

Finally, the tool formats the result so it’s readable and shareable. By default it shows:

• The converted value (rounded to a sensible number of decimals).
• The exact formula used (so you can trust it).
• A quick interpretation like “freezing” or “very hot” based on common benchmarks.

That last piece is intentionally designed for virality: people love sharing a conversion when it’s tied to a meaningful label. “It’s 35°C (95°F) — no wonder I’m melting” is more shareable than “35°C = 95°F.”

Tips to avoid conversion mistakes

• Don’t mix up temperature and temperature change: A change of 10°C equals a change of 10 K, but that does not mean 10°C equals 10 K.
• Remember the anchors: 0°C = 32°F and 100°C = 212°F. These two points catch most errors fast.
• Watch Kelvin: Kelvin can’t be negative. If you see negative Kelvin, something went wrong.
• Cooking conversions are approximate: Ovens vary. Rounding to the nearest 5°F (or 5°C) is often plenty.
• Weather conversations can be rounded: 20°C ≈ 68°F is “nice.” Nobody needs 68.36°F in casual talk.

If you’re doing lab work or engineering, you’ll want more precise rounding rules. This converter keeps a balance: accurate enough for real use, but not so many decimals that it becomes unreadable.

Frequently Asked Questions

• What’s the easiest way to convert Celsius to Fahrenheit?

  Use °F = (°C × 9/5) + 32. Multiply by 1.8, then add 32. For quick mental math, remember that 0°C = 32°F and 10°C ≈ 50°F.

• Why is 32 involved in Fahrenheit conversions?

  Fahrenheit chose a scale where water freezes at 32°F (and boils at 212°F at sea level). Because Celsius freezes at 0°C, converting between them requires shifting by 32.

• Is Kelvin the same as Celsius but with a different starting point?

  Basically, yes. Kelvin uses the same step size as Celsius, but its zero is at absolute zero. That’s why K = °C + 273.15.

• Can Kelvin be negative?

  In standard thermodynamics, Kelvin cannot be negative. If you input a negative Kelvin value, this converter will flag it as invalid.

• Does altitude affect boiling point conversions?

  The conversion math stays the same, but the boiling point of water changes with pressure/altitude. At higher altitudes, water boils below 100°C (212°F). The calculator converts units — it doesn’t model pressure effects.

• Why do my results show decimals?

  Because Fahrenheit and Celsius use different degree sizes. Many values convert into repeating decimals (like 1/9). The tool rounds to keep things readable while staying accurate for practical use.

• Is this temperature converter accurate?

  Yes for standard unit conversion. The formulas used are the widely accepted definitions for Celsius, Fahrenheit, and Kelvin. If you need instrument-level precision, consider measurement uncertainty and calibration — but the math itself is correct.

Common temperatures (for context)

Conversions feel more useful when you have “anchors.” Here are a few well-known reference points so you can quickly interpret your result. Think of this as a mental cheat sheet.

• 0°C / 32°F / 273.15 K: water freezes
• 10°C / 50°F / 283.15 K: cool day
• 20°C / 68°F / 293.15 K: comfortable
• 30°C / 86°F / 303.15 K: hot day
• 100°C / 212°F / 373.15 K: water boils (sea level)

• 37°C / 98.6°F / 310.15 K: average body temperature
• 38°C / 100.4°F / 311.15 K: often used fever threshold
• 60°C / 140°F: hot enough to scald skin quickly (use caution)

If you’re using the converter for safety (hot water, cooking oil, industrial work), always follow local safety guidelines. Temperature numbers are only one part of the risk picture.