A cup of jam is 320 g — the USDA figure, measured spooned and levelled. Fruit preserves set with sugar and pectin. It is used for toast, baking, glazes and thumbprint cookies. It is the heaviest ingredient on this page at 320 g per cup, because it is mostly sugar and fruit, and that density is the first thing to know: a cup of jam is a serious amount of sweetness, which is why recipes measure it in spoonfuls, and why the amount you spread on toast or fold into a cake decides whether the result is balanced or cloying. This guide covers the weight of jam in every measure you will use — cups, tablespoons and teaspoons — how to measure it correctly, what to use instead when you run out, and how to store it. All weights on this page are approximate; verify with a kitchen scale when the recipe matters.
Jam: weight and measurement table
The table below gives the weight of Jam in every measure you will use, from a teaspoon up to 2 cups, all derived from the USDA figure of 320 g per cup, spooned and levelled. Every figure is approximate — spooned and levelled is a technique, not a machine setting — so when the recipe matters, weigh the ingredient on a kitchen scale instead.
| Amount | Weight (approx.) |
|---|---|
| 1 teaspoon | 6.7 g |
| 1 tablespoon | 20 g |
| 1/4 cup (4 tbsp) | 80 g |
| 1/3 cup | 106.7 g |
| 1/2 cup (8 tbsp) | 160 g |
| 3/4 cup (12 tbsp) | 240 g |
| 1 cup (16 tbsp) | 320 g |
| 2 cups | 640 g |
| 100 g | 0.31 cups |
There are 3 teaspoons in a tablespoon and 16 tablespoons in a cup, so you can move between any of these measures by multiplying or dividing. If a recipe calls for 100 g and you only have measuring cups, that is about 0.31 cups. Keep the cups to grams converter open while you cook and you will never need to do the arithmetic in your head.
What is Jam?
Fruit preserves set with sugar and pectin. Jam is used for toast, baking, glazes and thumbprint cookies. The ingredient is a familiar one in most kitchens, but it is worth knowing what it actually is before you measure it, because the form it comes in decides how it behaves in a recipe. Jam as sold is the form the weight on this page refers to: 320 g per cup, spooned and levelled, from USDA. If you buy it in a different form — chopped, ground, toasted, sweetened or unsweetened — the weight per cup changes, sometimes by a lot, so weigh the ingredient in the form the recipe asks for, or weigh it before you change its form. That single habit, weighing before chopping, grinding or toasting, is what keeps the recipe consistent from one bake to the next.
How to measure Jam
Spoon the jam lightly into the measuring cup or spoon, then level the top with the back of a knife. Do not scoop the measure straight from the bag or the jar, because scooping packs the ingredient down and adds weight with every spoonful. Do not press it down or shake the measure to settle it, because that packs it too. The spooned and levelled method is a technique, not a machine setting, so two people measuring the same ingredient can still differ by a few grams, which is why the figures on this page are approximate. When the recipe matters, weigh the jam on a kitchen scale instead: put the bowl on the scale, press tare, and add the jam until the scale reads the weight you need.
How to store Jam
Refrigerate after opening; use within 3 months. That storage advice is worth following, because jam goes stale faster than most cooks expect, and stale jam will spoil a whole batch of baking. Keep it sealed, because air and moisture are what make it go stale, and keep it away from strong smells, because it absorbs odours from the cupboard. Check the ingredient before you use it: smell it, taste a little, and look at it. If it smells sharp, stale or off, or if it has changed colour or texture, replace it rather than risking a recipe on it. A small amount of fresh jam is always better than a large amount of stale jam, and the cost of replacing it is far less than the cost of a ruined bake.
What to use instead of Jam
If you run out of jam, the closest swaps are Honey at 336 g per cup. Swap by weight, not by volume, because the cup weights differ, and a volume swap gives the wrong amount. Each substitute changes the flavour a little, so choose the one that suits the dish: a mild substitute for a delicate bake, and a stronger one where the flavour can carry it. Taste the finished dish before serving, because a substitute that works in a salad may not work in a cake, and the other way round.
Worked examples: Jam in real recipes
1. A Victoria sponge with strawberry jam
A Victoria sponge for afternoon tea uses 8 tablespoons of jam, about 160 g, spread over one layer before the cream goes on. The jam gives the cake its sweetness and its fruit flavour, and the weight is what decides whether the cake is balanced or cloying: too much jam and the cake turns sticky and sweet, too little and it tastes plain. Spread the jam evenly to the edges, but keep it away from the very edge, so it does not squeeze out when the top layer goes on.
2. A glaze for a fruit tart
A fruit tart glaze uses 6 tablespoons of jam, about 120 g, warmed gently with a little water and brushed over the fruit. The jam gives the tart its shine and seals the fruit, keeping it fresh and glossy, and the weight is what decides the thickness: too much jam and the glaze turns sticky, too little and it barely coats the fruit. Warm the jam until it loosens, brush it on thinly, and let it set before serving.
3. Thumbprint cookies for a bake sale
A batch of thumbprint cookies uses 4 tablespoons of jam, about 80 g, spooned into the thumbprint of each cookie before baking. The jam melts in the oven and gives the cookies their sweet centre, and the amount matters: a small teaspoonful per cookie is enough, and too much bubbles over and burns on the tray. Use a firm jam that holds its shape, and spoon it in just before the cookies go into the oven.
Why the weight of Jam matters
Jam matters by weight because it is almost pure sugar, and a small error changes a recipe's sweetness a lot. In a thumbprint cookie, the jam filling decides whether the cookie is sweet or cloying, and the difference can be a single teaspoon. In a glaze, the jam adds sweetness and shine, and too much makes the glaze sticky and overpowering. The cup measure is unreliable because jam is thick and clings to the sides of the measure, so a scooped cup can be 20 g heavier than a spooned and levelled one. Weighing it keeps the sweetness consistent, and it also matters because jams vary in sugar content: a low-sugar jam weighs less per cup and tastes less sweet, so the same volume gives a different result. The fruit matters too: a tart jam like blackcurrant needs less sugar elsewhere than a sweet jam like strawberry.
The USDA figure, and how it was measured
The USDA figure for jam is not disputed: 320 g per cup, spooned and levelled, is the accepted value, and other sources agree within a few grams. Small differences between brands and batches are normal, because natural ingredients vary, but the variation is small enough that the figure on this page is a reliable guide for everyday cooking. The figure on this page, 320 g per cup, was measured spooned and levelled, which is the standard method for this kind of ingredient. If you measure it differently — scooping instead of spooning, packing instead of levelling, or measuring after chopping — the weight changes, and the recipe changes with it. The source matters too: USDA is the reference used throughout this site, because its figures are consistent and widely used in baking, and the USDA figures are used where King Arthur does not publish one. When two sources disagree, this site says so, and the figure given is the one judged most reliable for everyday cooking.
Common mistakes with Jam
The most common mistake is using jam straight from the jar in a glaze without warming it first: cold jam is thick and lumpy, and it does not spread evenly. Warm it gently until it loosens, then brush it on. The second mistake is using too much jam in a thumbprint cookie, where it bubbles over in the oven and burns on the tray; use a small teaspoonful per cookie. The third mistake is storing opened jam in the cupboard, where it goes mouldy quickly; refrigerate it and use it within three months. Finally, do not use jam as a substitute for fresh fruit in a cake: jam is far sweeter and wetter, and the cake will turn out heavy and cloying.
Frequently asked questions
How many grams is 1 cup of jam?
One cup of jam weighs about 320 g, spooned and levelled, using the USDA figure. That is for jam as sold, and the weight is the highest on this page, because jam is mostly sugar and fruit. Most recipes need only a few tablespoons, so the tablespoon weight of about 20 g is the number that matters most. The figure is approximate, so verify with a kitchen scale when the recipe matters.
How many tablespoons is 100 grams of jam?
100 grams of jam is about 5 tablespoons, spooned and levelled, because one tablespoon weighs about 20 g. Five level tablespoons is exactly 100 g, which makes jam one of the easiest ingredients to measure by spoon. Weigh it on a scale for baking, because the jam clings to the spoon and a heaped spoon can be much heavier.
Can I use jam instead of fresh fruit in baking?
It is better not to. Jam is far sweeter and wetter than fresh fruit, so a cake made with jam instead of fruit turns out heavy and cloying. Jam works best as a filling, a topping or a glaze, where its sweetness and its shine are the point, rather than as a replacement for fresh fruit in a batter.
How long does jam keep after opening?
Refrigerate it after opening and use it within 3 months. Opened jam goes mouldy quickly at room temperature, and even in the fridge it does not last forever. If you see mould on the surface, throw the whole jar away, because the mould can spread through the jam even if you scrape it off.
Why does my jam glaze turn sticky?
Because too much jam was used, or it was not warmed enough before brushing. Warm the jam gently with a little water until it loosens, then brush it on thinly in a single layer. A thick layer of jam stays sticky and never sets properly, while a thin layer dries to a glossy shine.