My consultant said this is not always accurate. I think it's a fairly good guide though providing there's no free food allowance in the said item. I always syn at 20 calories per syn & it's not harmed me.
When there is no free food in the product it is 1 syn per 20 calories - that's how the calculator works it out. When there *is* free food to factor in you need to use the syns calculator/syns online.