Homemade soda syrup calculator: ratio and syrup per glass

Soda syrup ratios, explained

A syrup ratio is sugar to water by weight. A 1:1 "simple" syrup is half sugar; a 2:1 "rich" syrup is two-thirds sugar and pours thicker; a 1:2 "light" syrup is a third sugar. Weighing matters because a cup of sugar and a cup of water weigh different amounts: USDA FoodData Central puts a cup of granulated sugar at 200 g, while a cup of water is about 237 g.

Once dissolved, the syrup is denser than water, so a millilitre of it carries more sugar than you might guess. Using the density of sugar solutions measured by the US National Bureau of Standards, this is what each strength holds:

Richer syrup is not sweeter per gram of sugar; it just packs the same sugar into less liquid. That is handy for keeping more fizz in the glass, since every millilitre of syrup is a millilitre less of cold, carbonated water. For a fizzy soda that stays lively, see the carbonation calculator for the pressure your sparkling water needs.

How much syrup per glass of sparkling water?

Pour the syrup first, then the cold sparkling water, and stir once. Between 15 and 30 ml of 1:1 syrup in 200 to 250 ml of fizz suits most flavours; bold ones such as ginger or winter spice carry further than delicate citrus. The calculator gives the dilution as syrup to water, so 30 ml to 220 ml shows as 1 : 7.3.

For scale, USDA FoodData Central lists regular cola at 9.94 g of sugars per 100 g, which is 36.8 g in a 12 fl oz (355 ml) can, or about 26 g per 250 ml. A 30 ml pour of 1:1 syrup in the same 250 ml glass has about 18 g.

Flavour and acid

Warm the sugar and water together until clear, take the pan off the heat, add the flavouring and leave it to steep as it cools, then strain into a clean bottle. Zest gives fragrance without bitterness if you take only the coloured layer; thin slices of fresh ginger give more bite the longer they steep. Juice in a flavour is counted as part of the water, and its own sugar from FoodData Central is added to the total.

Citric acid gives the clean sourness that makes a soda taste like a soda rather than sweet water. Because it is set as a percentage of the syrup's weight, it scales with the batch: 1 % of a 500 g batch is 5 g. Add it after the syrup has cooled a little, stir until dissolved, and taste a diluted glass before adding more.

Worked examples

• Lemon soda, 1:1 syrup: 250 g sugar, 190 g water and 60 ml lemon juice make about 406 ml of syrup at 50.3 % sugar. 30 ml per glass with 220 ml of fizz gives 18.6 g of sugar, and the batch fills 13 glasses.
• Same syrup, capped at 10 g: switch to low-sugar mode and the calculator pours 16 ml per glass, a 1 : 13.6 dilution. Add more zest or ginger to the syrup so the weaker glass still tastes of something.
• Rich ginger syrup: 250 g sugar and 125 g water with 100 g sliced ginger; 20 ml per glass with 230 ml of fizz gives 17.7 g of sugar.

Sugar per glass against the guidance

Sugar from a syrup counts as free sugars for the NHS and the World Health Organization, and as added sugars in the US Dietary Guidelines. The NHS says adults should have no more than 30 g of free sugars a day, children aged 7 to 10 no more than 24 g, and children aged 4 to 6 no more than 19 g. The WHO recommends keeping free sugars below 10 % of energy and suggests that going below 5 %, roughly 25 g a day, brings further benefits. The Dietary Guidelines for Americans, 2025–2030, say no amount of added sugars is recommended, that one meal should contain no more than 10 g, and that sugar-sweetened drinks are best avoided.

The card shows a glass against each of those, as a guide rather than a target: they are whole-day or whole-meal figures, not allowances for one drink. The same guidelines also advise limiting low-calorie sweeteners, so the low-sugar mode here works by pouring less, not by swapping sugar for a sweetener. This is general information, not medical or dietary advice.

Common mistakes

• Measuring the ratio by volume. A cup of sugar weighs less than a cup of water, so a "1:1" by cups comes out weaker than 1:1 by weight.
• Boiling the syrup hard. Water boils off and the syrup gets stronger than its ratio; warm it only until the sugar dissolves.
• Forgetting the juice. Orange juice adds sugar of its own; the calculator includes it, but a free-pour of extra juice does not.
• Pouring fizz onto a warm syrup. Warm liquid holds less gas, so the glass goes flat faster; keep syrup and water cold.

Making fruit syrups to keep, rather than a quick soda base? Jelly Glimmer's jam, pectin and canning calculators are made for that. For cooking with the leftover syrup, try MealWhim.