Unit Converters
Fahrenheit to Celsius: Worksheet and Answer Key
Work six Fahrenheit-to-Celsius practice questions, compare readings with temperature differences, and use an answer key that shows each arithmetic step.
Practice the reverse direction
For each reading, subtract 32 first, multiply the result by 5, and divide by 9. Try these six Fahrenheit values without looking at the answer key: 32, 50, 68, 95, 14 and −40. Keep a separate line for the subtraction so a sign error is visible. These questions deliberately include zero Celsius, everyday positive values and negative values. Write the Celsius unit after each final answer; simply copying the original Fahrenheit unit would make an otherwise correct calculation ambiguous.
Check the first three answers
For 32°F, subtracting 32 gives zero, so the answer is 0°C. For 50°F, the difference is 18, and 18 × 5/9 gives 10°C. For 68°F, the difference is 36, producing 20°C. Notice that Fahrenheit increases by 18 between these readings while Celsius increases by 10. A completed worksheet should preserve that pattern. If your first answer is 17.777... rather than zero, you probably multiplied by 5/9 without first subtracting the scale offset.
Check the last three answers
For 95°F, the intermediate difference is 63 and the result is 35°C. For 14°F, subtracting 32 gives −18 and the answer is −10°C. For −40°F, the difference is −72 and multiplying by 5/9 returns −40°C. Negative inputs should remain signed throughout the calculation. Do not remove a minus sign just because the number represents a temperature; negative readings are valid on both Celsius and Fahrenheit scales, and the arithmetic determines whether the converted result is positive or negative.
Add two extension questions
First convert 72°F: subtracting 32 gives 40, so C = 200/9 = 22.222...°C, approximately 22.2°C to one decimal place. Then find the Celsius change represented by a rise from 50°F to 86°F. The Fahrenheit difference is 36, corresponding to 20°C of change. The endpoints are 10°C and 30°C, which confirm that difference. Keep this extension separate from converting a reading of 36°F, whose answer would instead be about 2.22°C.
Keep the reading and the temperature change separate
A Celsius reading converts to Fahrenheit with F = 9C/5 + 32. In reverse, C = 5(F − 32)/9. The multiplication accounts for differently sized degrees; the addition or subtraction accounts for different zero points. A temperature difference has no zero-point shift: a rise of 10°C equals a rise of 18°F, while an actual reading of 10°C equals 50°F. State whether the question asks for a reading or a change before applying the formula. This distinction matters for laboratory changes, thermostat adjustments and comparisons between two measured temperatures.
Use the converter with explicit scale selections
The linked temperature tool has a numeric value and separate From and To scale selections. It also supports kelvin and Rankine, so verify both selections rather than relying on a remembered default. For kelvin, K = C + 273.15, and the scale symbol is K without a degree sign. Celsius and Fahrenheit can legitimately have negative readings. For ordinary thermodynamic temperature calculations, values below 0 K are outside the model. The converter changes the representation of a supplied temperature; it does not measure an object or predict how quickly it will heat.
Preserve the arithmetic until the last step
Carry the subtraction and multiplication through with their unrounded values, then round to a precision justified by the original measurement. A thermometer marked in whole degrees does not acquire hundredth-degree accuracy when its reading is converted. To reverse-check an answer, put the unrounded result into the opposite formula and confirm that it returns the starting value. Small discrepancies after a round trip usually come from intermediate rounding. A large discrepancy, such as confusing 212°F with 212°C, usually comes from the selected direction or from omitting the 32-degree offset.
Calculator for the supported step
Enter the stated reading in the value field, select its original scale under From and the requested scale under To, then calculate. The worked arithmetic below gives an independent check of the selected direction.
Sources and method
Related guides
Apply F = 9C/5 + 32 to convert Celsius a Fahrenheit, keep parentheses in the reverse formula, and verify positive, negative and decimal examples.
Use an exact Celsius–Fahrenheit formula, compare it with a mental shortcut, and calculate how much error the shortcut introduces at different readings.
Build a Celsius–Fahrenheit comparison table from one linear rule, interpolate between reference pairs, and distinguish equal readings from equivalent temperatures.