Temperature Converter
25°C equals 77°F, and 0°C equals 32°F. A temperature converter turns a reading in Celsius, Fahrenheit, or Kelvin into the equivalent value on a different scale. Enter a value, choose the source scale, choose the target scale, and the tool applies the correct temperature equation instead of a plain multiplication factor. Temperature scales do not share a common zero point, so an accurate conversion needs both a multiplication step and an addition or subtraction step, unlike converting a length or a weight. This temperature converter is useful for reading a weather forecast from another country, following a recipe written in Fahrenheit while your oven only displays Celsius, checking a lab reading in Kelvin, or converting a thermostat setting, travel packing list, or classroom worksheet from one scale to another without doing the arithmetic by hand.
Quick answer
Celsius to Fahrenheit multiplies by 9/5 (or 1.8) and adds 32. For example, 25°C is (25 x 9/5) + 32 = 77°F.
What this tells you
- •Celsius to Fahrenheit multiplies by 9/5 (or 1.8) and adds 32. For example, 25°C is (25 x 9/5) + 32 = 77°F.
- •Fahrenheit to Celsius subtracts 32 first, then multiplies by 5/9. For example, 98.6°F is (98.6 - 32) x 5/9 = 37°C.
- •Kelvin never goes negative because 0 K is absolute zero. Convert Kelvin to Celsius by subtracting 273.15, and convert back by adding 273.15.
- •-40 is the one point where Celsius and Fahrenheit show the same number, since (-40 x 9/5) + 32 = -40.
- •The converter rounds the number shown on screen, but the calculation itself always runs on the full, unrounded formula.
How to Use
- 1Enter the temperature value you want to convert. Positive numbers, negative numbers, and decimals are all supported.
- 2Select the source scale (Celsius, Fahrenheit, or Kelvin) that matches your starting reading.
- 3Select the target scale you want the value converted into.
- 4Click Calculate to see the converted temperature, along with the source scale, target scale, and the conversion formula used.
- 5Check the sign on negative values carefully. Fahrenheit and Celsius negative ranges do not match up until you reach -40, so a small input mistake can flip a result from cold to mild.
How It Works
Formula
Celsius to Fahrenheit: F = (C x 9/5) + 32. Fahrenheit to Celsius: C = (F - 32) x 5/9. Celsius to Kelvin: K = C + 273.15.This temperature converter treats Celsius as the base scale. For a Fahrenheit or Kelvin starting value, it first converts to Celsius, then converts from Celsius to whatever target scale you picked. Converting Celsius to Fahrenheit multiplies by 9/5 and adds 32, because each Fahrenheit degree is smaller than a Celsius degree and the two scales start counting from different zero points (0°C is 32°F). Converting to Kelvin only needs addition, since a Kelvin degree is the same size as a Celsius degree and the scales differ only by a fixed 273.15 offset, which is absolute zero expressed in Celsius. Because temperature formulas mix multiplication with addition or subtraction, you cannot convert temperature with a single ratio the way you can convert length, weight, or volume.
Calculation note: values are processed in the order shown above, using the current input units.
Worked Examples
Celsius to Fahrenheit: comfortable room temperature
Multiply 25 by 9/5 to get 45, then add 32 for a result of 77°F. This is a common comparison when a thermostat or weather app displays Celsius but you think in Fahrenheit.
Fahrenheit to Celsius: normal body temperature
Subtract 32 from 98.6 to get 66.6, then multiply by 5/9 for exactly 37°C. This is the figure most commonly cited as average human body temperature on the Celsius scale.
Celsius to Fahrenheit: oven baking temperature
Multiply 180 by 9/5 to get 324, then add 32 for 356°F. Recipes written for European ovens often list Celsius settings that need converting for US-style Fahrenheit dials.
Fahrenheit to Celsius: a hot summer day
Subtract 32 from 100 to get 68, then multiply by 5/9 for 37.777...°C, which rounds to 37.78°C. Many heat-advisory thresholds in Fahrenheit-based forecasts sit near this range.
Celsius to Kelvin: the freezing point of water
Kelvin conversion is addition only, so 0°C plus the 273.15 offset gives 273.15 K. This value anchors the Kelvin scale and shows why Kelvin has no negative readings for ordinary weather.
Kelvin to Celsius: a lab notebook reading
Subtract the 273.15 offset from 310.15 K to get 37°C, the same body-temperature figure from the Fahrenheit example above. Lab equipment and scientific papers often report readings in Kelvin, so this conversion is common when checking a result against a Celsius or Fahrenheit reference.
Common mistakes
- Applying only a multiplication factor. Temperature scales are not a simple ratio like inches to centimeters, so skipping the +32/-32 step or the 273.15 offset produces a value that looks close but is wrong.
- Doing the steps out of order for Fahrenheit to Celsius. Subtract 32 first, then multiply by 5/9. Multiplying first and subtracting 32 afterward gives a different, incorrect number.
- Assuming a Kelvin result can be negative. Kelvin has no negative values because 0 K is absolute zero, the coldest temperature physically possible, so a negative Kelvin output usually means the wrong source scale was selected.
- Forgetting the -40 crossover point. Celsius and Fahrenheit only match at -40, so assumptions about which scale reads higher near freezing do not hold for extreme cold readings.
- Rounding an intermediate step before finishing the calculation. Rounding partway through a Fahrenheit-to-Celsius or Celsius-to-Kelvin conversion compounds a small error, which matters if the rounded figure feeds into another calculation.
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