To convert body temperature from Fahrenheit to Celsius, subtract 32 and multiply by 5/9. To go from Celsius to Fahrenheit, multiply by 1.8 and add 32. So 98.6 deg F is 37 deg C. The NHS calls 38 deg C (100.4 deg F) or above a high temperature. This page converts numbers only and is not a diagnosis.
Temperature in degrees Celsius
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How to Use the Body Temperature Converter
- Choose the unit on your thermometer, then type the reading. The answer appears in the other unit as you type.
- Pick who was measured. This only changes which NHS advice the colour band quotes. It does not change the converted number.
- Read the converted value and the band under it. Use the chart further down if you want a printable table.
In this guide, deg C means degrees Celsius and deg F means degrees Fahrenheit. The tool itself shows the degree sign.
| Result | What it tells you |
|---|---|
| Temperature in degrees Celsius or Fahrenheit | Your reading in the other unit, from the exact NIST relation. |
| Same reading on every scale | Fahrenheit, Celsius and kelvin side by side. |
| Distance from the 38 deg C line | How far the reading sits below or above 38 deg C (100.4 deg F), the NHS high-temperature line. |
| Where it sits against published ranges | Which published band the number falls in: below 35 deg C, below usual, usual, above usual, or at or above 38 deg C. |
| Reverse check | The answer converted back, to prove the round trip. |
| Bulk list | Each pasted reading converted, in order. |
| Verdict band | One sentence quoting the published threshold that applies, with a pointer to NHS advice. It is not a diagnosis. |
What Is Body Temperature Conversion?
Body temperature conversion restates a thermometer reading on the other scale, Fahrenheit or Celsius. The temperature itself does not change. Only the number and the unit change.
People need it when the thermometer, the doctor, the school form or the health website uses a different scale from the one they know. A US thermometer reads in Fahrenheit. The NHS and most of the world quote Celsius. A reading of 38.5 on one scale means something very different from 38.5 on the other, so the unit matters as much as the number.
MedlinePlus, a US National Library of Medicine service, says the average normal body temperature is generally accepted as 98.6 deg F (37 deg C). It adds that some studies show a range from 97 deg F (36.1 deg C) to 99 deg F (37.2 deg C), and that it varies by person, age, activity and time of day. The NHS adult page says normal body temperature is different for everyone and changes during the day.
This page does not diagnose a fever, a cause or a risk. It converts the number and shows which published threshold the number meets. A clinician decides what it means for a person.
How Does the Body Temperature Conversion Formula Work?
Fahrenheit and Celsius use different zero points and different degree sizes. Water freezes at 0 deg C and 32 deg F, and one Celsius degree equals 1.8 Fahrenheit degrees. NIST SP 811 Appendix B writes the relation exactly.
deg C = (deg F - 32) x 5/9 | deg F = (deg C x 9/5) + 32 | K = deg C + 273.15- Fahrenheit to Celsius: subtract 32, then multiply by 5/9. For 100.4 deg F: 100.4 - 32 = 68.4, and 68.4 x 5/9 = 38 deg C.
- Celsius to Fahrenheit: multiply by 1.8, then add 32. For 38.5 deg C: 38.5 x 1.8 = 69.3, and 69.3 + 32 = 101.3 deg F.
- Check by going back. 101.3 - 32 = 69.3, and 69.3 / 1.8 = 38.5.
The order matters: subtract first when you start in Fahrenheit, multiply first when you start in Celsius. Both 1.8 and 32 are exact, so no rounding happens until the display. For other scales see the full temperature converter hub.
Body Temperature Conversion Examples
The classic average. 98.6 deg F: 98.6 - 32 = 66.6, and 66.6 x 5/9 = 37 deg C. This is the figure MedlinePlus gives as the generally accepted average.
The NHS high-temperature line. The NHS adult and children pages both say a high temperature is 38 deg C or above. 38 x 1.8 = 68.4, and 68.4 + 32 = 100.4 deg F. MedlinePlus words it as a temperature over 100.4 deg F (38 deg C). The two sources differ only on whether exactly 38 counts.
A reading of 37.5 deg C. 37.5 x 1.8 = 67.5, and 67.5 + 32 = 99.5 deg F. It is above the 37.2 deg C top of the usual range MedlinePlus quotes, and below the 38 deg C line.
A reading of 39 deg C. 39 x 1.8 = 70.2, and 70.2 + 32 = 102.2 deg F. For a baby aged 3 to 6 months, the NHS children page says to call 111 at 39 deg C or higher.
The low end. 35 deg C is 95 deg F. The NHS defines hypothermia as a drop in body temperature below 35 deg C and calls it a medical emergency.
All of these were computed with exact fractions in code before they were written here.
Body Temperature Conversion Chart: Celsius to Fahrenheit
This chart runs from 35.0 to 42.0 deg C in 0.1 steps. Fahrenheit values are rounded to one decimal. Use the tool above for two decimals. To save a copy, use the Print button and choose Save as PDF in your print dialog.
Bold rows mark numbers quoted by the NHS or MedlinePlus: 35 (hypothermia line), 36.1 and 37.2 (ends of the usual range), 37 (average), 38 (NHS high-temperature line), 39 and 40.
| deg C | deg F | deg C | deg F | deg C | deg F |
|---|---|---|---|---|---|
| 35.0 | 95.0 | 37.4 | 99.3 | 39.8 | 103.6 |
| 35.1 | 95.2 | 37.5 | 99.5 | 39.9 | 103.8 |
| 35.2 | 95.4 | 37.6 | 99.7 | 40.0 | 104.0 |
| 35.3 | 95.5 | 37.7 | 99.9 | 40.1 | 104.2 |
| 35.4 | 95.7 | 37.8 | 100.0 | 40.2 | 104.4 |
| 35.5 | 95.9 | 37.9 | 100.2 | 40.3 | 104.5 |
| 35.6 | 96.1 | 38.0 | 100.4 | 40.4 | 104.7 |
| 35.7 | 96.3 | 38.1 | 100.6 | 40.5 | 104.9 |
| 35.8 | 96.4 | 38.2 | 100.8 | 40.6 | 105.1 |
| 35.9 | 96.6 | 38.3 | 100.9 | 40.7 | 105.3 |
| 36.0 | 96.8 | 38.4 | 101.1 | 40.8 | 105.4 |
| 36.1 | 97.0 | 38.5 | 101.3 | 40.9 | 105.6 |
| 36.2 | 97.2 | 38.6 | 101.5 | 41.0 | 105.8 |
| 36.3 | 97.3 | 38.7 | 101.7 | 41.1 | 106.0 |
| 36.4 | 97.5 | 38.8 | 101.8 | 41.2 | 106.2 |
| 36.5 | 97.7 | 38.9 | 102.0 | 41.3 | 106.3 |
| 36.6 | 97.9 | 39.0 | 102.2 | 41.4 | 106.5 |
| 36.7 | 98.1 | 39.1 | 102.4 | 41.5 | 106.7 |
| 36.8 | 98.2 | 39.2 | 102.6 | 41.6 | 106.9 |
| 36.9 | 98.4 | 39.3 | 102.7 | 41.7 | 107.1 |
| 37.0 | 98.6 | 39.4 | 102.9 | 41.8 | 107.2 |
| 37.1 | 98.8 | 39.5 | 103.1 | 41.9 | 107.4 |
| 37.2 | 99.0 | 39.6 | 103.3 | 42.0 | 107.6 |
| 37.3 | 99.1 | 39.7 | 103.5 |
Body Temperature Conversion Table: Fahrenheit to Celsius
This table runs from 95.0 to 107.0 deg F in 0.1 steps, with Celsius to two decimals. The bold rows are 95 (NHS hypothermia line), 97 and 99 (ends of the usual range MedlinePlus gives), 98.6 (average), 100.4 (high-temperature line), 102.2 and 104.
| deg F | deg C | deg F | deg C | deg F | deg C |
|---|---|---|---|---|---|
| 95.0 | 35.00 | 99.1 | 37.28 | 103.2 | 39.56 |
| 95.1 | 35.06 | 99.2 | 37.33 | 103.3 | 39.61 |
| 95.2 | 35.11 | 99.3 | 37.39 | 103.4 | 39.67 |
| 95.3 | 35.17 | 99.4 | 37.44 | 103.5 | 39.72 |
| 95.4 | 35.22 | 99.5 | 37.50 | 103.6 | 39.78 |
| 95.5 | 35.28 | 99.6 | 37.56 | 103.7 | 39.83 |
| 95.6 | 35.33 | 99.7 | 37.61 | 103.8 | 39.89 |
| 95.7 | 35.39 | 99.8 | 37.67 | 103.9 | 39.94 |
| 95.8 | 35.44 | 99.9 | 37.72 | 104.0 | 40.00 |
| 95.9 | 35.50 | 100.0 | 37.78 | 104.1 | 40.06 |
| 96.0 | 35.56 | 100.1 | 37.83 | 104.2 | 40.11 |
| 96.1 | 35.61 | 100.2 | 37.89 | 104.3 | 40.17 |
| 96.2 | 35.67 | 100.3 | 37.94 | 104.4 | 40.22 |
| 96.3 | 35.72 | 100.4 | 38.00 | 104.5 | 40.28 |
| 96.4 | 35.78 | 100.5 | 38.06 | 104.6 | 40.33 |
| 96.5 | 35.83 | 100.6 | 38.11 | 104.7 | 40.39 |
| 96.6 | 35.89 | 100.7 | 38.17 | 104.8 | 40.44 |
| 96.7 | 35.94 | 100.8 | 38.22 | 104.9 | 40.50 |
| 96.8 | 36.00 | 100.9 | 38.28 | 105.0 | 40.56 |
| 96.9 | 36.06 | 101.0 | 38.33 | 105.1 | 40.61 |
| 97.0 | 36.11 | 101.1 | 38.39 | 105.2 | 40.67 |
| 97.1 | 36.17 | 101.2 | 38.44 | 105.3 | 40.72 |
| 97.2 | 36.22 | 101.3 | 38.50 | 105.4 | 40.78 |
| 97.3 | 36.28 | 101.4 | 38.56 | 105.5 | 40.83 |
| 97.4 | 36.33 | 101.5 | 38.61 | 105.6 | 40.89 |
| 97.5 | 36.39 | 101.6 | 38.67 | 105.7 | 40.94 |
| 97.6 | 36.44 | 101.7 | 38.72 | 105.8 | 41.00 |
| 97.7 | 36.50 | 101.8 | 38.78 | 105.9 | 41.06 |
| 97.8 | 36.56 | 101.9 | 38.83 | 106.0 | 41.11 |
| 97.9 | 36.61 | 102.0 | 38.89 | 106.1 | 41.17 |
| 98.0 | 36.67 | 102.1 | 38.94 | 106.2 | 41.22 |
| 98.1 | 36.72 | 102.2 | 39.00 | 106.3 | 41.28 |
| 98.2 | 36.78 | 102.3 | 39.06 | 106.4 | 41.33 |
| 98.3 | 36.83 | 102.4 | 39.11 | 106.5 | 41.39 |
| 98.4 | 36.89 | 102.5 | 39.17 | 106.6 | 41.44 |
| 98.5 | 36.94 | 102.6 | 39.22 | 106.7 | 41.50 |
| 98.6 | 37.00 | 102.7 | 39.28 | 106.8 | 41.56 |
| 98.7 | 37.06 | 102.8 | 39.33 | 106.9 | 41.61 |
| 98.8 | 37.11 | 102.9 | 39.39 | 107.0 | 41.67 |
| 98.9 | 37.17 | 103.0 | 39.44 | ||
| 99.0 | 37.22 | 103.1 | 39.50 |
Fever Temperature Chart by Age: Thresholds Compared
Published sources give different numbers for different people. This table lists only what the named pages say, read on 2026-10-03. It does not add cut-offs of its own.
| Who | Number | What the source says | Source |
|---|---|---|---|
| Adults | 38 deg C (100.4 deg F) or above | Usually considered a high temperature, sometimes called a fever. You can feel hot or shivery below 38 deg C and still have one. Ask for an urgent GP appointment or call 111 if it is not getting better or is getting worse. | NHS, fever in adults |
| Children and babies | 38 deg C (100.4 deg F) or more | A high temperature. It usually returns to normal within 1 to 4 days. Call 111 if it has lasted 5 days or more, or if there are other signs of illness. | NHS, fever in children |
| Baby under 3 months | 38 deg C (100.4 deg F) or higher | Call 111, or if you think they have a high temperature. | NHS, fever in children |
| Baby 3 to 6 months | 39 deg C (102.2 deg F) or higher | Call 111, or if you think they have a high temperature. | NHS, fever in children |
| Any age | Below 35 deg C (95 deg F) | Hypothermia, a medical emergency treated in hospital. Go to A and E or call 999. | NHS, hypothermia |
| Usual range, adults and children | 36.1 to 37.2 deg C (97 to 99 deg F) | Some studies show this range around the 37 deg C (98.6 deg F) average. A temperature over 100.4 deg F (38 deg C) most often means a fever. | MedlinePlus |
The NHS children page also lists reasons to call 999 whatever the number, such as a stiff neck, a rash that does not fade under a glass, or a first fit. Read it in full if a child is unwell. It says not to give paracetamol to a child under 2 months and not to give aspirin to children under 16.
What Is a Normal Body Temperature in Celsius and Fahrenheit?
MedlinePlus gives 98.6 deg F (37 deg C) as the generally accepted average, with some studies showing 97 to 99 deg F (36.1 to 37.2 deg C). It says normal temperature varies by person, age, activity and time of day, and that in adults it is lowest in the early morning.
So a single reading above or below 37 deg C is not by itself a problem. 36.0 deg C is 96.8 deg F, just under the low end MedlinePlus quotes, and it is well above the 35 deg C hypothermia line. This tool labels such a reading as below the usual range and nothing more.
The NHS adult page adds that a thermometer is optional. It says you may have a high temperature if your chest or back feels hotter than usual, or if you feel shivery, even when a thermometer shows less than 38 deg C.
Factors That Change a Thermometer Reading
The conversion is exact, but the reading you convert depends on how it was taken.
The Type of Thermometer
The NHS adult page says to use a digital thermometer under the tongue or in the armpit. It says not to use a glass thermometer, because they can be dangerous, or forehead strips, because they are not accurate. It also warns that some infrared thermometers do not meet UK regulations. The NHS children page uses the armpit for children.
Recent Events
The NHS children page says a child who has just had a bath or been wrapped in a blanket may read higher for a short time. Wait a few minutes and try again.
Time of Day
MedlinePlus says adult body temperature is lowest in the early morning. Compare readings taken at the same time of day.
The Person
Both MedlinePlus and the NHS stress that normal differs from person to person. A baby, an adult and an older adult can all be well at different numbers.
Why This Tool Does Not Adjust for the Measuring Site
Many pages claim a fixed offset between the mouth, ear, forehead and armpit. The pages read for this guide give no such offset table, so the tool does not apply one. It converts your number as typed.
When to Use a Body Temperature Converter
A Thermometer in the Other Unit
Many digital thermometers can switch units, but not all. If yours shows Celsius and a form asks for Fahrenheit, convert once and write both down.
Reading Health Advice from Another Country
The NHS quotes Celsius. A US reader can paste the number in and see 100.4 deg F. A UK reader following a US article can do the reverse.
Keeping a Fever Log
Paste a list of readings into the bulk box to convert a day of readings in one go. Note the time and the way each was taken.
Travel and School Forms
Health forms abroad often ask for one unit only. Converting beforehand avoids a typing slip. For the plain two-way converters, see the Fahrenheit to Celsius converter and the Celsius to Fahrenheit converter.
Common Body Temperature Conversion Mistakes
1. Typing the Wrong Unit
37 deg F is 2.78 deg C, a freezing day, not a fever. If your number looks absurd, check the unit box first. The tool warns when a result is outside 25 to 45 deg C.
2. Adding 32 to a Change
A rise of 1.5 deg C is a rise of 2.7 deg F, not 34.7. The 32 belongs only to a reading, never to a difference.
3. Swapping 5/9 and 9/5
Use 5/9 when going to Celsius and 9/5 when going to Fahrenheit. 38 x 5/9 + 32 gives 53.1, which is nowhere near the true 100.4.
4. Treating 37.5 Deg C as a Fever
It is 99.5 deg F. It sits above the usual range MedlinePlus quotes but below the 38 deg C line the NHS uses.
5. Ignoring How the Reading Was Taken
A forehead strip, an ear reading and an armpit reading are not interchangeable. The NHS calls forehead strips inaccurate.
6. Using the Number Alone
The NHS stresses how a person looks and feels. A baby who seems very unwell needs help at any number.
Accuracy and Limitations
The conversion is exact because 1.8 and 32 are fixed by definition. The weak point is the reading you enter and how you interpret it.
What it calculates accurately
- Fahrenheit to Celsius and back, from the NIST relation
- The matching kelvin value
- Distance from the 38 deg C (100.4 deg F) line
- Which published NHS or MedlinePlus band the number meets
What it does not account for
- Thermometer error or the way a reading was taken
- The person, their illness, medicines or other symptoms
- Cut-offs for groups the cited pages do not cover, such as older adults
- Whether a reading needs treatment
How We Calculate Body Temperature Conversions
Frequently Asked Questions About Body Temperature Conversion
What is 98.6 deg F in Celsius?
98.6 deg F is exactly 37 deg C. Subtract 32 to get 66.6, then multiply by 5/9. MedlinePlus gives this as the generally accepted average body temperature.
What temperature is a fever in Celsius and Fahrenheit?
The NHS says a high temperature, sometimes called a fever, is 38 deg C or above, which is 100.4 deg F. MedlinePlus says a temperature over 100.4 deg F (38 deg C) most often means a fever.
Is 37.5 deg C a fever?
37.5 deg C is 99.5 deg F. It is above the 37.2 deg C top of the usual range MedlinePlus quotes, but below the 38 deg C line the NHS uses for a high temperature. How you feel matters too.
What is 39 deg C in Fahrenheit?
39 deg C is 102.2 deg F. For a baby aged 3 to 6 months, the NHS says to call 111 at 39 deg C or higher.
What is a normal body temperature in Celsius?
MedlinePlus gives 37 deg C as the generally accepted average, with some studies showing 36.1 to 37.2 deg C. It varies by person, age, activity and time of day.
Is 36 deg C too low for body temperature?
36 deg C is 96.8 deg F, just under the low end of 36.1 deg C that MedlinePlus quotes. The NHS hypothermia line is below 35 deg C. This page cannot say what it means for one person.
At what temperature should I call about a baby?
The NHS says to call 111 for a baby under 3 months at 38 deg C (100.4 deg F) or higher, and for a baby of 3 to 6 months at 39 deg C (102.2 deg F) or higher. It also lists signs that need a 999 call at any number.
How do I convert body temperature from Fahrenheit to Celsius by hand?
Subtract 32, then multiply by 5/9. For 101.5 deg F: 101.5 - 32 = 69.5, and 69.5 x 5/9 = 38.61 deg C.
Does the tool change the result for mouth, ear or armpit readings?
No. The pages read for this guide give no offset table for measuring sites, so the tool converts the number as you type it and applies no site correction.
How do I convert body temperature in a spreadsheet?
For Fahrenheit in cell A2, type =(A2-32)*5/9 to get Celsius. For Celsius in A2, type =A2*1.8+32 to get Fahrenheit. Fill the formula down to convert a log.
Is my reading stored when I use the converter?
No. The maths runs in your browser. Saved results stay in your own browser storage until you clear them.
Sources
- Temperature relations for degree Fahrenheit, degree Celsius and kelvin (NIST SP 811, Appendix B.9, read 2026-10-03).
- High temperature (fever) in adults (NHS, 38 deg C line and thermometer advice, read 2026-10-03).
- High temperature (fever) in children (NHS, 38 deg C line, under 3 months and 3 to 6 months advice, read 2026-10-03).
- Hypothermia (NHS, below 35 deg C, read 2026-10-03).
- Body temperature norms (MedlinePlus, US National Library of Medicine, read 2026-10-03).
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Explore all health calculatorsThis page converts a temperature between Fahrenheit and Celsius and compares the number with published thresholds. It is not a diagnosis and not medical advice. If you or someone in your care is unwell, or you are worried about a reading, see a clinician or call your local emergency number. Spotted an error? Let us know.
Author
Shakeel Muzaffar is the Founder and Editor-in-Chief of MultiCalculators.com, bringing over 15 years of experience in digital publishing, product strategy, and online tool development. He leads the platform's editorial vision, ensuring every calculator meets strict standards for accuracy, usability, and real-world value. Shakeel personally oversees content quality, formula verification workflows, and the platform's commitment to publishing tools that are genuinely useful for students, professionals, and everyday users worldwide.
