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Is this bottle going to be safe?

The pressure a given carbonation level reaches at a given temperature, against what common closures and bottles will actually hold.

Bottle pressure

Pressure rises steeply with temperature. Check the warmest place the bottle will sit, not the coolest.

Pressure in the bottle

1.9 bar

In psi: 28 psi

This is an estimate from a model, not a measurement.

How this is worked out
  1. Carbonation: 2.50 volumes of CO₂
  2. At temperature: 20.0 °C
  3. Gauge pressure: about 1.9 bar (28 psi)
What this assumes (4)
  • Pressure rises steeply with temperature. A bottle that is comfortable in a cold cellar can be at twice the pressure in a warm room, which is why over-carbonated bottles fail in summer rather than in winter.
  • Bottle strength varies by design, maker, age and condition. About 4 bar is a common rule of thumb for crown-capped beer bottles; sparkling-wine bottles are built for more; a still-wine bottle is not a pressure vessel at all. Check the manufacturer’s rating — none of these figures is a guarantee.
  • This figure is for the temperature you entered. Pressure rises steeply with warmth, so a batch that is comfortable here can be past a closure rating in a hot room — check it at the warmest temperature the bottles will ever reach rather than at the one they are at now.
  • This is an approximation intended to show whether a figure is near a limit, not a certification of any particular container.
Bottle pressure against carbonation and temperatureGauge pressure inside a sealed bottle for one to six volumes of carbon dioxide, at three storage temperatures.Bottle pressure, bar (gauge)0246123456Volumes of CO₂beyond a plain corkneeds a sparkling bottle20 °C12 °C5 °C
Gauge pressure inside a sealed bottle for one to six volumes of carbon dioxide, at three storage temperatures.
Described in full
What is plotted
Volumes of dissolved carbon dioxide run along the horizontal axis, from one to six. Gauge pressure in bar runs up the vertical axis. Three curves are drawn, one each for 5 °C, 12 °C and 20 °C, distinguished by dash pattern as well as by label.
Temperature is not a small effect
The three curves diverge sharply. Three volumes of gas exerts roughly one bar at 5 °C, about one and three-quarter bar at 12 °C, and about two and a half bar at 20 °C — the same liquid, the same bottle, more than double the pressure.
Why carbon dioxide behaves this way
Its solubility falls as temperature rises. Warming a sealed bottle does not create gas; it drives dissolved gas out of solution into the headspace, where it registers as pressure.
The plain cork line
A dashed reference marks the region beyond what an unwired straight cork in a still-wine bottle will hold. Above it a cork will creep and eventually push out, which is the least bad of the possible outcomes.
The sparkling bottle line
A second reference marks where a pressure-rated sparkling bottle with a wired or crown closure becomes necessary. Traditional-method cider and perry sit above this line at cellar temperature and well above it at room temperature.
The practical safety point
A bottle conditioned to a safe pressure in a cool cellar can be carrying twice that pressure after a day in a warm room or a car. Bottle-conditioned cider should be primed for the warmest temperature it will ever see, not the coolest.
How the curves are calculated
From the solubility of carbon dioxide in water at each temperature: pressure is the dissolved volume divided by the solubility, less one atmosphere for the surrounding air. The figures are close approximations, and cider is not pure water.

What the numbers mean in practice

About 4 bar is a common rule of thumb for a sound crown-capped beer bottle, not a manufacturer’s rating and not a guarantee: bottles differ, and reused or scratched glass is weaker. A Champagne bottle is built for considerably more and is the right container for a traditional-method cider. A still-wine bottle is not a pressure vessel at all, and carbonating in one is the single most common way home producers get hurt.

Pressure rises steeply with temperature, which is why over-carbonated bottles fail in summer rather than in winter. Work from the warmest place the bottles will actually sit, not the cellar you are storing them in today.

Related tools

Where this reading comes from

Guides that reach this calculator, and what the number decides once you have it.