Temcon - Temperature Converter
Temcon is a focused Celsius and Fahrenheit converter. Enter a temperature in one field, tap the convert button between them, and the other field fills in to two decimal places. The formulas are shown on screen, so you can see exactly how the number was worked out.
It is handy for recipes and oven settings from another country, weather forecasts while travelling, body temperature readings on an imported thermometer, aquarium or pool temperatures, and science homework. A colour badge gives a quick feel for the value, from blue for freezing through green and orange to red for very hot.
Your last five conversions are listed underneath, and the page works in any browser with nothing to install.
The app runs entirely in your browser. What you enter is saved only on this device.
How to use Temcon
- Enter a temperature. Type a value in the Celsius field, or clear it and type in the Fahrenheit field instead. Negative numbers and decimals are accepted.
- Convert. Tap the arrows button between the two fields. The other field is filled in and the colour badge updates.
- Convert the other way. If both fields contain numbers, Celsius is used as the input. Use the clear (x) button on the Celsius field before converting from Fahrenheit.
- Check the formulas. The Formula card shows °F = (°C × 9/5) + 32 and °C = (°F − 32) × 5/9.
- Reuse earlier results. The History card lists your last five conversions. Tap the restore icon on a row to load it again, or the bin icon to clear the list. The refresh button at the top resets both fields.
Features
- Celsius to Fahrenheit and Fahrenheit to Celsius
- Results to two decimal places
- Accepts values from absolute zero (−273.15 °C) to 1000 °C
- Colour cue from cold to very hot
- Formulas shown on screen
- History of the last five conversions
- Clear buttons and a reset button
Understanding Celsius and Fahrenheit
Two scales, two reference points
The Celsius scale puts the freezing point of water at 0 °C and its boiling point at 100 °C at sea level, so a degree is one hundredth of that range. The Fahrenheit scale sets freezing at 32 °F and boiling at 212 °F, a range of 180 degrees. That is why one Celsius degree equals 1.8 Fahrenheit degrees, and why the conversion needs both a multiplication and an offset of 32.
The formulas
To go from Celsius to Fahrenheit, multiply by 9/5 (1.8) and add 32. To go from Fahrenheit to Celsius, subtract 32 and multiply by 5/9. Order matters: subtracting before multiplying gives a very different answer from multiplying first. Conveniently, the two scales meet at −40, where −40 °C equals −40 °F.
Quick mental estimates
For a rough Celsius to Fahrenheit figure, double the Celsius value and add 30: 20 °C becomes about 70 °F, close to the exact 68 °F. Going the other way, subtract 30 and halve. The shortcut drifts at extremes, so use the exact formula for cooking, medicine or science.
Useful reference temperatures
Normal body temperature is often quoted as 37 °C, or 98.6 °F. A comfortable room is around 20 to 22 °C (68 to 72 °F). A hot summer day of 35 °C is 95 °F. Common oven settings are 180 °C (356 °F, usually rounded to 350 °F) and 200 °C (392 °F, often 400 °F). Fridges are kept below about 5 °C, roughly 41 °F.
Absolute zero and Kelvin
Nothing can be colder than absolute zero, −273.15 °C or −459.67 °F, which is why Temcon does not accept lower values. Scientists often use the Kelvin scale, which starts at absolute zero and uses the same step size as Celsius: add 273.15 to a Celsius value to get kelvins.
Frequently asked questions
Why did my Fahrenheit value change back?
When both fields contain numbers, Temcon converts from Celsius. Clear the Celsius field first, then enter your Fahrenheit value and convert.
What range of temperatures can I convert?
From absolute zero (−273.15 °C or −459.67 °F) up to 1000 °C (1832 °F). Values outside that range are set to the nearest limit.
Is my history saved?
No. The last five conversions are kept only while the page is open and are cleared when you reload or close it. Nothing is stored or uploaded.
Does Temcon support Kelvin?
Not directly. Add 273.15 to the Celsius result to get kelvins.
How precise are the results?
Results are calculated exactly and shown rounded to two decimal places, which is more precision than kitchen or weather thermometers usually provide.
Does it need an internet connection?
Only to load the page. Conversions are calculated in your browser.
What is different from the phone app?
The converter is the same. The iPhone and Android apps show ads that a subscription removes; the web version has no ads or purchases.
Limitations of the web version
- Celsius and Fahrenheit only; no Kelvin field
- When both fields are filled, conversion always starts from Celsius
- History is cleared when the page is reloaded
- Upper limit of 1000 °C
Phone app
Temcon is also available as an app for phones and tablets: