Water’s boiling point in Celsius is 100 °C at sea level; elevation and air pressure change the exact temperature.
If you’re chasing a precise number for kitchen timing, lab work, or outdoor cooking, here’s the straight answer: at standard atmospheric pressure near sea level, liquid water turns to vapor at 100 °C. Go higher in altitude, the air gets thinner, the pressure drops, and the boiling point slips below 100 °C. Go lower than sea level or use a pressure cooker, the boiling point climbs.
Boiling Point Of Water In Celsius — Quick Reference
Use the table below as a fast guide. It shows typical boiling temperatures at common elevations. These figures assume clear weather and standard pressure for those heights. Real readings can drift a little with daily weather swings and your exact location.
| Elevation | Approx. Pressure (kPa) | Boiling Temp (°C) |
|---|---|---|
| Sea level (0 m) | 101.3 | 100.0 |
| 300 m / 1,000 ft | 97.0–98.0 | 99.1–99.4 |
| 600 m / 2,000 ft | 93.0–94.0 | 98.1–98.6 |
| 900 m / 3,000 ft | 89.5–90.5 | 97.1–97.7 |
| 1,500 m / 5,000 ft | 84–85 | 95.0–95.6 |
| 2,000 m / 6,600 ft | 79–80 | 93.3–94.0 |
| 2,500 m / 8,200 ft | 75–76 | 92.0–92.5 |
| 3,000 m / 9,800 ft | 70–71 | 90.0–90.5 |
| 4,000 m / 13,100 ft | 62–63 | 86.5–87.5 |
| 5,000 m / 16,400 ft | 54–55 | 82.5–83.5 |
Why 100 °C At Sea Level Is The Benchmark
Boiling begins when vapor pressure at the liquid’s surface matches the pressure of the air above it. At sea level, that air pressure sits near 1 atm (101.325 kPa). Under this load, pure water reaches that match point at 100 °C, which is why 100 °C is the standard taught in school and used in calibration tasks.
Change the pressure and you shift the match point. Lower air pressure means the liquid needs less heat to build bubbles that rise and break. Higher pressure makes bubbles harder to form, so the temperature climbs before rolling bubbles appear.
Altitude, Weather, And Daily Swings
Elevation isn’t the only variable. Weather fronts nudge barometric pressure up or down by a few kPa. That can move the boiling point by a fraction of a degree. A strong low-pressure system will shave the temperature a bit; a high-pressure day will add a touch. The shift won’t wreck dinner, but it matters when you chase tight lab readings or candy-making stages.
Purity, Salt, And Dissolved Stuff
Pure water hits the values you see in textbooks. Add dissolved minerals or a pinch of salt and the boiling point edges upward. In a home kitchen, a spoon of salt in a pot changes flavor and speeds seasoning, but the temperature gain is tiny. A briny solution or sugar syrup, on the other hand, can bump the temperature enough to matter in confectionery work.
Pressure Cookers And Sealed Systems
A sealed pot raises internal pressure. That lets the liquid run hotter than 100 °C while still staying liquid. A typical pressure cooker set to 15 psi gauge (about 2 atm absolute) pushes water near 121 °C. This is why tough cuts soften fast and dried beans cook in less time. The flip side is safety: use the device as directed and let pressure drop before opening the lid.
Rolling Boil, Gentle Boil, And Simmer
Heat level also shapes the surface. A rolling boil throws steady, large bubbles and steam. A gentle boil shows smaller, steady bubbles with less splash. A simmer gives small, lazy bubbles with quiet movement. All three can sit near the same temperature; the difference is the rate of energy input and vapor release. When a recipe asks for a simmer, it’s asking for control, not a new temperature.
Kitchen Uses Where A Degree Or Two Matters
Egg timing, candy stages, and coffee extraction care about temperature peaks. At altitude, a soft-boiled egg needs extra time because the pot tops out below 100 °C. Sugar work is even touchier, since each stage maps to a narrow range on the thermometer. Coffee brewers that report water near 96 °C can read low in mountain towns.
Safety: Boiling To Make Water Safer To Drink
When local notices advise boiling tap water, heat treatment helps reduce microbes that cause illness. Public health guidance recommends bringing water to a rolling boil for a set time and then letting it cool. For full instructions and time/altitude notes, refer to the CDC boil water advisory. Follow local directions if they differ, since they reflect your system’s conditions.
Measurement Tips For Accurate Readings
Pick The Right Thermometer
A fast digital probe is the easiest pick in a home kitchen. Clip-on candy thermometers work for deep pots and sugar stages. In a lab, use properly calibrated glass or digital instruments with traceable certificates.
Place The Probe Correctly
Keep the tip submerged but off the metal bottom and away from the side. Strong bubbling can cause the tip to peek into steam pockets, which reads high or low depending on splash and placement.
Mind Calibration
You can check a thermometer with two points. The low point is an ice-water bath (0 °C with a slushy mix). The high point is a full rolling boil at your location’s pressure. Mark any offset or adjust the unit if it allows.
Celsius, Fahrenheit, And Kelvin
Most kitchen and science tasks in many countries use Celsius. Conversions are quick:
- Fahrenheit = (C × 9/5) + 32
- Kelvin = C + 273.15
At sea level, that means 100 °C equals 212 °F and 373.15 K. A readout near 95 °C in a mountain town might look odd until you recall the lower local pressure.
Why Bubbles Form: A Short Look At The Physics
Inside the pot, tiny pockets of vapor try to form at microscopic surface scratches or on bits of dust. When the liquid’s vapor pressure reaches the air pressure above the pot, those pockets grow instead of collapsing. Heat adds energy, molecules break free more often, and the bubble column turns steady. That’s the rolling boil you see.
Common Myths That Create Confusion
“Bigger Flame Raises The Boiling Temperature”
More flame adds energy and creates a stronger boil, but the temperature at boiling stays near the same point for that pressure. The extra energy goes into turning liquid to vapor rather than pushing the temperature higher.
“Salt Makes Pasta Water Much Hotter”
A small handful shifts the boiling point by a tiny fraction of a degree. Big changes need very high salt concentration, which most cooks don’t use for pasta.
“Steam Is Always Hotter Than The Boiling Liquid”
Right above the surface, steam and liquid share the same temperature at equilibrium. Superheated steam in sealed systems can run hotter, but that’s a different setup.
Altitude Cooking Adjustments That Actually Work
If you live or travel at elevation, plan tweaks for timing and equipment. A lid helps trap heat and reduces evaporation loss. A pressure cooker offsets thin air by lifting the boiling point. Some tasks need longer time, not extra flame. Use this guide to tune your routine.
For deep reference values on water across pressures and temperatures, the NIST Chemistry WebBook entry for water provides tables and formulas used in labs and engineering.
Practical Adjustments By Height
The figures below group common kitchen tasks at different elevations. Times refer to the stage after the liquid reaches a steady boil.
| Elevation | Boiling Temp (°C) | Adjustment Guide |
|---|---|---|
| 0–600 m | 98.5–100 | Follow standard recipes; candy stages and coffee extraction match sea-level charts. |
| 600–1,500 m | 95–98.5 | Add 5–10% time for eggs, grains, and legumes; check candy stages with a thermometer, not a cold-water test. |
| 1,500–2,500 m | 92–95 | Use a lid often; add 10–20% time; a pressure cooker restores tenderness for beans and braises. |
| 2,500–3,500 m | 88–92 | Add 20–30% time; candy work benefits from precise digital readings; consider pressure for stews. |
| 3,500–5,000 m | 82–88 | Plan major time increases; pressure cooking becomes the default for legumes and tough cuts. |
Troubleshooting: Your Kettle Stops At 97–99 °C
Smart kettles and espresso boilers use sensors placed in specific spots. Steam pockets, rapid bubbling, or a control algorithm can produce a reading that looks a tad low. If you live on a hill or in a mountain town, the device may be correct for your air pressure. A quick check: bring a pot to a strong boil and hold a probe in the middle of the liquid. Compare the readout with the altitude table above.
How To Calibrate With A Two-Point Check
Ice Bath Method
Fill a cup with crushed ice and cold water. Stir for a minute. Insert the probe so the tip sits in the slush, not pressed to an ice chunk. It should read 0 °C. Note any offset.
Local Boil Method
Bring a pot to a rolling boil. Hold the probe off the bottom and read the temperature. Compare the reading with the elevation table. Mark the offset on the thermometer or store the correction in your head.
When You Need Absolute Precision
Most home tasks tolerate small swings. If you need tight control for research, brewing profiles, or industrial checks, measure local barometric pressure and compute the boiling temperature with a formula or a trusted reference table. A lab-grade sensor and a pressure-aware calculator give you repeatable values day to day.
Frequently Missed Details That Matter
Mineral Scale In The Pot
Scale deposits can trap tiny bubbles and change the way boiling looks, which tempts cooks to crank heat harder than needed. Descale kettles and boilers on a schedule for stable behavior.
Lid Use And Evaporation
A lid cuts heat loss and keeps the surface calm. That helps reach a steady boil faster and limits evaporation in long cooks.
High Sugar Loads
Syrups rise above the local boiling point of pure water. That is the whole point of candy stages. Use a reliable thermometer and avoid splashing on the probe tip during rapid bubbling.
Key Takeaways
At standard pressure near sea level, the boiling point reads 100 °C. Thin air at higher elevations lowers that number. A pressure cooker pushes it higher. Small amounts of salt barely shift the reading; heavy solute loads do. For safe drinking during advisories, follow public health directions and hold a rolling boil for the stated time. For accuracy, pick a good thermometer, place it well, and use the two-point check to confirm your device. When precision matters, match your method to your local pressure or use a sealed system to set the temperature you need.