Convert Temperature
Choose input scale and output scale, then set formatting options.
Download & History
No conversions saved yet. Run a conversion to populate the history table.
Example Data Table
These examples demonstrate typical conversions and expected outputs.
| Input | From | To | Expected Output |
|---|---|---|---|
| 0 | Celsius (°C) | Fahrenheit (°F) | 32 |
| 100 | Celsius (°C) | Kelvin (K) | 373.15 |
| -40 | Fahrenheit (°F) | Celsius (°C) | -40 |
| 300 | Kelvin (K) | Rankine (°R) | 540 |
| 80 | Réaumur (°Re) | Celsius (°C) | 100 |
Formula Used
This calculator converts From → Kelvin → To. Using Kelvin as a base keeps conversions consistent and reduces formula branching.
- K = C + 273.15
- K = (F − 32) × 5/9 + 273.15
- K = R × 5/9
- K = Re × 5/4 + 273.15
- C = K − 273.15
- F = (K − 273.15) × 9/5 + 32
- R = K × 9/5
- Re = (K − 273.15) × 4/5
Absolute zero checks are performed by verifying that Kelvin is not negative.
How to Use This Calculator
- Enter a temperature value using digits, decimals, or scientific notation.
- Select the input scale in the From menu.
- Select the output scale in the To menu.
- Set decimal precision and an optional rounding mode.
- Press Convert to see the result above the form.
- Optionally export your conversion history to CSV or PDF.
Scale Coverage and Reference Points
This calculator converts five common scales: Celsius, Fahrenheit, Kelvin, Rankine, and Réaumur. Use reference points to sanity‑check results: water freezes at 0°C, 32°F, 273.15 K, and 491.67°R; water boils at 100°C, 212°F, 373.15 K, and 671.67°R. Another quick check is −40°, where Celsius and Fahrenheit match exactly.
Kelvin as a Mathematical Pivot
All conversions are routed through Kelvin to keep the math consistent. Converting From → Kelvin uses one formula per scale, then Kelvin → To uses another. That structure reduces branching, prevents mismatched constants, and makes it easier to validate limits such as K ≥ 0 before any final formatting is applied.
Precision Controls and Rounding Modes
Precision can be set from 0 to 10 decimals, which is useful for classroom problems and lab reporting. Standard rounding is best for general work, while floor and ceil are helpful when you must stay conservative in bounds calculations. For example, 98.6°F becomes 37.0°C at one decimal, but 37.0000°C at four decimals. Enable trimming to remove trailing zeros.
Absolute Zero Validation and Data Quality
Temperatures below absolute zero are physically invalid, so the tool checks the Kelvin value after conversion. Key limits are 0 K, −273.15°C, −459.67°F, and 0°R. If an entered value maps to K < 0, the calculator blocks the result and asks for corrected input. Réaumur is also supported, where 80°Re corresponds to 100°C.
Session History, Exports, and Reproducibility
Each successful conversion is logged with timestamp, input, output, and precision settings. The history table supports quick review and is capped at 200 rows to stay fast. CSV export is ideal for spreadsheets, while the PDF report preserves a clean, printable record for assignments or documentation. Clear history anytime to start a fresh dataset.
Reading the Conversion Curve
The Plotly chart visualizes how the target scale changes around your input using a small range and evenly spaced points. Because temperature conversions are linear, the curve is a straight line; the slope is 9/5 when converting °C to °F and 5/9 for the reverse. The highlighted marker shows your exact conversion on that line.
FAQs
1) Which temperature scales are included?
You can convert between Celsius, Fahrenheit, Kelvin, Rankine, and Réaumur. Pick a From scale and a To scale, then submit to compute the converted value.
2) Why does the calculator use Kelvin internally?
Kelvin provides a single baseline where absolute zero is 0. Converting through Kelvin reduces formula branching and makes it easy to validate impossible inputs before displaying results.
3) How should I choose precision and rounding?
Use 0–2 decimals for quick checks and 3–6 for lab-style reporting. Standard rounding fits most needs; floor and ceil are helpful when you must stay conservative for limits or tolerances.
4) What triggers the absolute zero warning?
If your entry converts to a Kelvin value below 0, the input is physically invalid for that scale. Adjust the value or verify you selected the correct unit.
5) What gets saved in history and exports?
Each successful run stores timestamp, input, units, output, and precision. The CSV downloads a spreadsheet-friendly log, and the PDF generates a printable report from the same session history.
6) What does the Plotly graph represent?
It plots the target scale against the source scale around your input using evenly spaced points. The line is linear for temperature conversions, and the highlighted marker shows your exact conversion.