How to Make Jam: A Complete Beginner's Guide

What jam is, and why it sets

Jam is fruit cooked with sugar until it thickens into a spreadable gel. Four things work together to make that happen:

Fruit. It supplies flavor, natural pectin and acid. Ripe fruit has good flavor; slightly underripe fruit tends to have more pectin. Apples, citrus peel, currants and many tart fruits are usually described as higher in pectin, while strawberries, peaches and blueberries are usually described as lower.
Pectin. This is the substance that forms the gel. It comes from the fruit itself or from a commercial pectin you add.
Sugar. Sugar helps pectin set, helps preserve color and texture, and contributes to the keeping quality of the jam.
Acid. Pectin needs some acidity to gel properly. Lemon juice is the usual way to top up a low-acid fruit.

Understanding these four pieces makes it much easier to follow a recipe, and to work out what went wrong when a batch does not behave.

Choose your method

There are three common routes, and they are not interchangeable in terms of how long the jam keeps.

Refrigerator jam. Cooked fruit and sugar, stored in clean jars in the fridge. It is the simplest option and needs no canning equipment, but it is only for short-term storage, so make small batches. Recipes usually give a fridge life of a few weeks or less; follow the one in your recipe.
Freezer jam. Often no-cook, made with a special pectin and kept in the freezer. It tastes very fresh. See our guide to no-cook freezer jam.
Water-bath canned jam. Cooked jam in jars processed in a boiling water canner so it can be stored in the pantry. This route needs a tested recipe and exact processing times (see below). For a worked example, try our Ball-style raspberry jam.

If this is your first batch, a small refrigerator batch is a low-risk way to learn how fruit behaves.

Equipment

A wide, heavy-bottomed pot (jam foams and rises, so leave room)
A long-handled spoon and a heat-safe spatula
A potato masher for crushing fruit
A few small plates kept in the freezer or fridge for the set test
Clean jars with lids
For canning: a boiling water canner (or a large pot with a rack), a jar lifter, a funnel and new flat lids

A candy or jam thermometer is optional but helpful. At sea level, the gel point is commonly given as about 220 degrees F (104 degrees C), which is roughly 8 degrees F above the boiling point of water. At higher altitudes, water boils at a lower temperature, so the target changes; the plate test is more reliable than a number there.

A basic stovetop jam (refrigerator style)

This is a general method, not a tested canning recipe. Do not process it in a water-bath canner. It is a widely used approach to fridge jam; the ratio below is a starting point and you can adjust to taste.

You will need

4 cups of chopped or crushed fruit (berries, or pitted and chopped stone fruit)
About 2 cups of sugar (more for tart fruit, a little less for very sweet fruit)
2 tablespoons of lemon juice

Method

Combine the fruit and sugar in a bowl and let them sit for 30 minutes to a few hours so the juices start to flow.
Put the plate in the freezer.
Scrape everything into a wide pot with the lemon juice. Heat gently, stirring, until the sugar dissolves.
Bring to a steady, vigorous boil, stirring often so it does not catch on the bottom. Skim off foam if you like.
Start testing for a set after about 10 to 15 minutes. Cooking time varies a lot with the fruit and the width of your pot.
When it passes the set test, take the pot off the heat and let it settle for a few minutes. This helps fruit pieces distribute evenly rather than floating to the top.
Ladle into clean jars, cool, then refrigerate.

How to tell when jam has set

Cold-plate test. Spoon a little jam onto a chilled plate, return it to the fridge or freezer for a minute, then push it with your finger. If it wrinkles and the line you drew stays open, it has set. If it runs back together, cook a little longer and test again. Take the pot off the heat while you test so it does not overcook.
Spoon test. Drops that merge into a sheet which hangs from the spoon, rather than dripping, suggest a set.
Thermometer. About 220 degrees F at sea level, with the altitude caveat above.

Jam thickens more as it cools, so aim for a loose, softly gelled texture in the pot rather than a firm one.

Will lemon juice thicken jam?

It can help, but it is not a thickener on its own. Pectin needs acid to gel, so adding lemon juice to a low-acid fruit such as strawberries or peaches can improve the set. However, if there is not enough pectin or the jam has not been cooked long enough, extra lemon juice will not fix it. When you are canning, use the amount of bottled lemon juice the tested recipe specifies rather than adding more or less.

Canning jam safely

If you want shelf-stable jars, follow a recipe that has been tested for canning, such as those from Ball or the National Center for Home Food Preservation (NCHFP). With canning, the fruit, sugar, pectin and acid amounts are all part of the safety and set, so avoid improvising on quantities of a tested recipe, and do not double a batch unless the recipe says you can.

General points that tested guidance agrees on:

Use clean, hot jars and new flat lids.
Leave the headspace the recipe specifies (often 1/4 inch for jam).
Wipe the rims, apply lids and bands fingertip-tight, and process for the full time in a boiling water canner.
Adjust processing time for your altitude according to the recipe or NCHFP’s chart.
Jars processed for 10 minutes or longer generally do not need separate sterilizing, but the recipe you follow comes first.
After cooling, check that each lid has sealed. Refrigerate any jar that has not, and use it first.

Common problems

Runny jam. Often not enough pectin, acid or cooking. Some runny jams firm up over a day or two, so wait before you fix it. If it is still loose, you can recook it, or simply call it a sauce and use it on yogurt or ice cream. For canned jars, use a tested remaking method rather than guessing.
Too stiff. Usually overcooked. Stir in a little warm juice or water and use it as a glaze, or spoon it onto cheese boards.
Can you boil jam for too long? Yes. Overcooking can darken the color, dull the flavor and produce a tough or sticky set, and pectin can break down if it is cooked for very long.
Foam. Harmless. Skim it, or stir in a tiny knob of butter if your recipe allows it.
Fruit floating. Let the jam cool for a few minutes in the pot and stir gently before jarring.
Crystals or graininess. Often undissolved sugar. Dissolve the sugar completely before boiling.

Storing jam

Properly processed, sealed jars are best kept in a cool, dark place. Quality is generally considered best within about a year.
Once opened, keep the jar in the refrigerator.
Refrigerator and freezer jams should be labeled with the date and used within the time given in the recipe.
If you see mold, discard the jar rather than scraping the top off. Also discard jars that have a bulging lid, an off smell or a leak.

What to do with jam

If you have more jars than toast, there are plenty of uses:

Swirl into yogurt, oatmeal or rice pudding.
Spread between layers of sponge cake or inside thumbprint cookies and hand pies; try jam drops, jam fingers or jam hamantaschen.
Warm and spoon over ice cream, pancakes or waffles.
Mix with a splash of vinegar or mustard as a glaze for roast pork or chicken.
Serve with cheese and crackers, as in a cheese ring with strawberry preserves.
Stir a spoonful into a vinaigrette or cocktail.
Use it at breakfast; see our jam breakfast recipes.

Strawberry jam in particular works well in sandwiches, jam bars, tarts and as a base for sauces.

Where to go next

A pectin-based canning recipe: Ball-style raspberry jam
A quick fridge jam using a pressure cooker: Instant Pot blueberry jam
Cutting down on sugar: sugar-free jam for canning
Skipping the stove: no-cook freezer jam
Something different: jam recipes with herbs, Illawarra plum jam and jam in the Thermomix