Fahrenheit to Celsius Converter

How to convert Fahrenheit to Celsius (the formula)

The formula is °C = (°F − 32) × 5/9. Subtract 32 to shift the scales onto a common zero, then multiply by 5/9 to shrink the Fahrenheit degree to a Celsius degree. Because a Fahrenheit degree is smaller, the Celsius number is always smaller than the Fahrenheit number (above −40).

Two examples: 100 °F → (100 − 32) × 5/9 = 68 × 5/9 = 37.78 °C. And 32 °F → (32 − 32) × 5/9 = 0 °C. The subtraction of 32 comes first, always; reversing the order gives a wrong answer.

This page converts live in both directions, so you can enter a Fahrenheit reading and watch the Celsius value update, or work the other way. That is handy for checking a US weather forecast against a metric thermometer, or converting an oven setting from a US recipe.

The quick mental math: subtract 30 and halve

For a fast estimate when you do not have a calculator, subtract 30 from the Fahrenheit value and divide by 2: °C ≈ (°F − 30) ÷ 2. For 72 °F that gives (72 − 30) ÷ 2 = 21, and the exact answer is 22.22 °C. For 100 °F it gives 35, close to the exact 37.78 °C.

The estimate works because the true step is subtracting 32 and multiplying by 5/9, and 5/9 is about 0.55 while the shortcut uses 0.5. It drifts a little at high temperatures but is good enough to decide whether you need a jacket. The +32 (or −32) offset is the part people forget, which is why the shortcut bundles it into a single "subtract 30" step.

If you want the estimate to be a bit more accurate, subtract 32 first and then halve: (72 − 32) ÷ 2 = 20, versus the exact 22.22 °C. Neither shortcut replaces the real formula, but both keep you oriented while you reach for the calculator on this page.

Fahrenheit to Celsius conversion chart

These are the Fahrenheit temperatures US users look up most, converted with the exact formula.

Anchor points: 32 °F is 0 °C, 68 °F is 20 °C, and 212 °F is 100 °C. Note that 98.6 °F converts to exactly 37 °C, a coincidence of the two scales that makes body temperature easy to remember.

Worked examples: weather, fever and oven settings

Four Fahrenheit-to-Celsius conversions with practical meaning.

• Weather: a 72 °F day is (72 − 32) × 5/9 = 22.22 °C, pleasant room temperature.
• Fever: 101 °F is (101 − 32) × 5/9 = 38.33 °C, a mild fever. The 100.4 °F threshold equals 38 °C.
• Baking: 350 °F is (350 − 32) × 5/9 = 176.67 °C, usually written as 180 °C in metric recipes.
• Deep frying: 375 °F is (375 − 32) × 5/9 = 190.56 °C.

The fever case shows why precision matters in medicine: a Fahrenheit reading of 100.4 is the widely used fever line, and that corresponds to 38.0 °C. Being a couple of degrees off in Fahrenheit can move you across a clinical threshold, so use the exact formula rather than the shortcut for health readings.

Fahrenheit to Celsius in cooking and travel

Two of the most common reasons US users convert Fahrenheit to Celsius are cooking and travel.

Cooking. A US recipe says 350 °F, but a metric oven or a foreign recipe works in Celsius. Converting gives 176.67 °C, which a metric cook rounds to 180 °C. Other common conversions: 325 °F = 162.78 °C, 375 °F = 190.56 °C, 400 °F = 204.44 °C and 425 °F = 218.33 °C. Because metric ovens step in 5 or 10 °C increments, rounding the exact value to the nearest mark is standard practice.

Travel. Weather apps in most countries default to Celsius. Converting a forecast of 90 °F gives 32.22 °C, so you know to pack for heat. Conversely, a European forecast of 15 °C is (15 × 1.8 + 32) = 59 °F, a cool day. Getting the direction right is the key: this page handles both, so you never convert the wrong way.

For meat safety, note that the US Department of Agriculture's 165 °F poultry minimum equals 73.9 °C, so any conversion used for food safety should use the exact formula, not an estimate.

Common Fahrenheit-to-Celsius mistakes

Most Fahrenheit-to-Celsius errors come from the order of operations or a reversed factor.

• Multiplying before subtracting. Always subtract 32 first, then multiply by 5/9. Doing it in the other order gives a wrong answer.
• Using 9/5 instead of 5/9. That is the Celsius-to-Fahrenheit direction, which makes the number bigger. Going F to C shrinks the value.
• Treating the halving shortcut as exact. "Subtract 30, halve" is a rough estimate; it can be several degrees off and should never be used for medicine or baking.
• Forgetting that below −40 the relationship flips. Fahrenheit reads colder than Celsius below −40, so the "Fahrenheit number is always bigger" rule has an exception.

Quick check: 212 °F should convert to 100 °C. If it does not, your formula is wrong.

Fahrenheit to Celsius: the full oven chart

Oven conversions are the single most common Fahrenheit-to-Celsius lookup in US kitchens, and rounding to a metric oven's nearest mark is normal practice.

Metric ovens usually step in 5 or 10 °C, so the "typical setting" column rounds the exact conversion to the nearest mark. For most baking, a few degrees either way makes no difference. The exceptions are candy-making and lean-bread baking, where a 5 °C swing can change the result, so use the exact converted value and a reliable oven thermometer for those. Always convert the recipe's stated temperature before applying any fan-oven reduction.

Sources: NIST SP 811, Guide for the Use of the International System of Units (SI), BIPM SI Brochure (the official definition of the SI), NIST SI Units reference.

Where these conversion factors come from

The relationship between the Fahrenheit and Celsius scales is fixed by international agreement rather than by local convention. The values used on this page follow the NIST guide to the SI (US Department of Commerce) and the BIPM SI Brochure, the two documents that define the exact values used worldwide.

Because these factors are exact by definition rather than measured, converting a number and converting it back always returns the number you started with, there is no rounding drift to worry about.