---
title: "Headspace: what it means in cooking — Tiny Plates"
description: "Headspace is the empty gap between the food and the lid of a jar or container. The right amount helps canning jars seal and stops frozen jars cracking."
url: "https://www.tinyplates.dev/glossary/headspace"
---

# Headspace

Headspace is the empty gap between the food and the lid of a jar or container. The right amount helps canning jars seal and stops frozen jars cracking.

Headspace is the space left between the top of the food, or its liquid, and the lid of a jar or container. In canning, the right headspace lets the jar form a vacuum seal. In freezing, it gives food room to expand as it freezes, since water grows by about 10 percent when it turns to ice.

## How to do it

1. Fill the hot jar with food and liquid, leaving the headspace your recipe asks for.
2. Slide a plastic or wooden spatula down the inside of the jar to release trapped air bubbles.
3. Measure again with a ruler or headspace tool, and add or remove food or liquid to correct it.
4. Wipe the rim clean, then put on the lid.

Tested US canning guidance uses these typical figures. Always follow the exact headspace in your recipe.

| Food                                  | Headspace               |
| ------------------------------------- | ----------------------- |
| Jams and jellies                      | 6 mm (1/4 inch)         |
| Fruit, tomatoes, pickles and relishes | 13 mm (1/2 inch)        |
| Low-acid foods for pressure canning   | 2.5 cm (1 inch) or more |

For freezing liquids such as soup or stock, leave about 13 mm (1/2 inch) in a wide-topped 500 ml (pint) container and 2.5 cm (1 inch) in a 1 liter (quart) one. Narrow-necked containers need more.

## Why it works

During [water bath canning](https://www.tinyplates.dev/glossary/water-bath-canning) or [pressure canning](https://www.tinyplates.dev/glossary/pressure-canning), the food expands and air is pushed out of the jar. As the jar cools, the contents shrink and pull the lid down into a seal. With too little headspace, food bubbles out under the lid and stops it sealing. With too much, not enough air is driven out, the jar may not seal, and food at the top can darken.

## Common mistakes

* Guessing the headspace instead of measuring.
* Skipping the air-bubble step. Bubbles rise during processing and change the headspace.
* Overfilling jars of liquid for the freezer. They crack as the liquid expands.
* Leaving a large gap in freezer containers of solid food, which causes [freezer burn](https://www.tinyplates.dev/glossary/freezer-burn).

## In recipes

Canning recipes say "leave 1/2-inch headspace" or "fill to within 1 cm of the rim". A jar that fails to seal must be refrigerated and eaten soon, or reprocessed with a new lid. Correct headspace is one part of safe canning; low-acid foods also need pressure canning to prevent [botulism](https://www.tinyplates.dev/glossary/botulism).

## Related terms

* [Water bath canningWater bath canning preserves high-acid foods like jam, pickles and acidified tomatoes by boiling sealed jars. It is not safe for low-acid foods.](https://www.tinyplates.dev/glossary/water-bath-canning)
* [Pressure canningPressure canning heats sealed jars to about 116°C (240°F) under steam pressure. It is the only safe home method for low-acid foods such as vegetables.](https://www.tinyplates.dev/glossary/pressure-canning)
* [Sterilize jarsSterilizing jars means heating clean glass jars to kill microbes before you fill them with jam or pickles. Boiling them for 10 minutes is the tested way.](https://www.tinyplates.dev/glossary/sterilize-jars)
* [BotulismBotulism is a rare but serious illness caused by a toxin that grows in low-acid, airless food, such as badly home-canned vegetables or garlic in oil.](https://www.tinyplates.dev/glossary/botulism)
* [Freezer burnFreezer burn is the dry, grayish, leathery patches on frozen food left exposed to air. It is safe to eat but tastes and feels worse, so trim it off.](https://www.tinyplates.dev/glossary/freezer-burn)

[More in food safety and storage](https://www.tinyplates.dev/glossary/category/food-safety)[Every term from A to Z](https://www.tinyplates.dev/glossary)