Quick answer: One ounce is 28.35 g, so for baking 4 oz is 113 g, 8 oz is 227 g and 1 lb is 454 g. Many British recipes round an ounce down to 25 g for convenience. That works if you round every ingredient the same way, because the proportions stay intact and the bake is simply about 12% smaller.
Handwritten recipe cards, older cookbooks and many classic cake recipes are written in ounces, while modern scales default to grams. This chart gives the exact figure, a practical rounded figure and the old 25 g shortcut side by side, so you can choose how precise to be. It is part of our weight conversions collection.
Ounces to grams chart for baking
“Practical” values are rounded to the nearest gram under 2 oz and to the nearest 5 g above that, which suits a digital kitchen scale. The last column shows the convenience rule of 25 g per ounce.
| Ounces | Exact grams | Practical grams | 25 g rule |
|---|---|---|---|
| ¼ oz | 7.1 g | 7 g | 6 g |
| ½ oz | 14.2 g | 14 g | 12.5 g |
| 1 oz | 28.3 g | 28 g | 25 g |
| 1½ oz | 42.5 g | 43 g | 37.5 g |
| 2 oz | 56.7 g | 55 g | 50 g |
| 3 oz | 85.0 g | 85 g | 75 g |
| 4 oz (¼ lb) | 113.4 g | 115 g | 100 g |
| 5 oz | 141.7 g | 140 g | 125 g |
| 6 oz | 170.1 g | 170 g | 150 g |
| 7 oz | 198.4 g | 200 g | 175 g |
| 8 oz (½ lb) | 226.8 g | 225 g | 200 g |
| 9 oz | 255.1 g | 255 g | 225 g |
| 10 oz | 283.5 g | 285 g | 250 g |
| 12 oz (¾ lb) | 340.2 g | 340 g | 300 g |
| 14 oz | 396.9 g | 395 g | 350 g |
| 16 oz (1 lb) | 453.6 g | 455 g | 400 g |
| 24 oz (1½ lb) | 680.4 g | 680 g | 600 g |
| 32 oz (2 lb) | 907.2 g | 905 g | 800 g |
Should you use 25 g or 28 g per ounce for baking?
Either works, as long as you use the same rule for every ingredient in the recipe. Baking depends on ratios. If the butter, sugar, flour and liquid are all scaled by 25 ÷ 28.35, they all shrink by the same 11.8%, so the mixture behaves the same and only the quantity changes.
Problems start when the rules are mixed. Converting the flour exactly but the butter with the 25 g shortcut leaves the dough with roughly 12% less fat than intended, enough to change the texture of pastry or shortbread. Eggs are the other catch: they are counted, not weighed, so a recipe scaled down by 12% still has the same number of eggs. For a large bake, or a recipe with several eggs, use the exact or practical column.
How do you convert an old recipe from ounces to grams?
Convert every weighed ingredient with the same factor, then check the result against the tin size. What you need:
- A digital kitchen scale that reads in grams
- The recipe, with any fluid ounces and spoons noted separately
- The chart above, or the converter in our grams to ounces guide
- Pick one column. Use “Practical grams” for a faithful result, or the 25 g rule if you are happy with a slightly smaller bake.
- Convert the dry and solid ingredients. Flour, sugar, butter, dried fruit and chocolate all use the weight ounce.
- Treat liquids separately. “Fl oz” is a volume: one UK fluid ounce is 28.41 ml, so 10 fl oz of milk is 284 ml, half a UK pint.
- Leave spoons alone. A UK teaspoon is 5 ml and a tablespoon is 15 ml, whatever system the rest of the recipe uses.
- Write the grams on the card. Next time you will not need to convert.
A worked example: a classic sponge written as 4 oz butter, 4 oz caster sugar, 4 oz self-raising flour and 2 eggs. Exact conversion gives 113 g of each, practical rounding gives 115 g, and the 25 g rule gives 100 g. All three keep the butter, sugar and flour at 1:1:1. With the 100 g version the two eggs make up a slightly larger share of the mix, so the batter will be a little looser; check it towards the end of the baking time.
What about very small amounts?
Below about half an ounce, weigh in grams and do not round down to the 25 g rule. Raising agents, salt and yeast are used in small quantities where a couple of grams matters. A quarter ounce is 7.1 g, close to the 7 g in a standard UK sachet of fast-action dried yeast. Most kitchen scales are least accurate at very low weights, so for a few grams a set of measuring spoons can be more reliable.
If you have no scale, our guide to measuring 100 g of flour without scales explains spoon-based methods. American recipes in cups need a different approach, covered in our UK vs US cup measurement guide.
Frequently asked questions
How many grams is 4 oz of flour?
4 oz of flour is 113.4 g, usually rounded to 115 g. Using the 25 g rule it would be 100 g.
How many grams is 8 oz of butter?
8 oz of butter is 226.8 g, so about 227 g. A standard 250 g block is 8.8 oz.
Why do some recipes say 1 oz equals 25 g?
25 g is a convenient round number close to 28.35 g. If every ingredient is converted the same way, the proportions stay the same and the bake is about 12% smaller.
Is an ounce of flour the same as a fluid ounce?
No. An ounce of flour is a weight of 28.35 g. A fluid ounce is a volume of 28.41 ml, and a fluid ounce of flour weighs much less than an ounce.
How many grams are in a pound for baking?
One pound is 453.6 g, usually rounded to 454 g or 455 g. The 25 g rule gives 400 g.
Sources
- Weights and Measures Act 1985, section 1: the pound as 0.45359237 kg, from which the ounce (one-sixteenth of a pound) follows.
- National Physical Laboratory: UK measurement standards.