I couldn’t find the answer online so I measured it myself. I’m not a food blogger so I’m allowed to provide the information without a rambling story about my childhood.
Imperial sizes are in brackets – I’m aware a lot of people still measure cakes in inches. 114g boxes of Cadbury Fingers contain 22 fingers as of November 2022 – if you find a different number in yours leave a comment and I’ll check whether this has changed.
| Shape | Size | Number of fingers | Number of boxes |
| Round | 10cm (4″) | 30 (31) | 2 |
| 15cm (6″) | 45 (46) | 3 | |
| 20cm (8″) | 60 (61) | 3 | |
| 25cm (10″) | 74 (76) | 4 | |
| 30cm (12″) | 89 (91) | 5 | |
| Square | 10cm (4″) | 38 (39) | 2 |
| 15cm (6″) | 57 (58) | 3 | |
| 20cm (8″) | 76 (77) | 4 | |
| 25cm (10″) | 94 (96) | 5 | |
| 30cm (12″) | 113 (115) | 6 |
If you need to calculate a different size or shape of cake, work out the perimeter length in centimeters and multiply by 0.94 (rounding up). Divide by 22 (again rounding up) to work out how many boxes you need. This is a conservative estimate to ensure that you will have enough fingers, you may well need less – I found that they aren’t actually a uniform size, there’s a surprising amount of variation between individual biscuits. All my working is in this spreadsheet – feel free to take a copy and adapt for your needs.
If you’re cooking around other people or likely to succumb to temptation yourself then you may also wish to factor in thievery. In my case, I lost three fingers during baking to people pinching them in passing, with a further half box eaten by Dan once I said I was done.
Here’s the cake we made, for the record.
