I am sure there used to be a recipe section on the website where you could list your ingredients and it would then calculate the syn value per portion. I think I used to be able to do something similar on MyFitnessPal to calculate calories but I am convinced I used to do the same on SlimmingWorld Online.
Please tell me I am not going mad and it was on there at one time!!!
Long time SW member, but I don't recall seeing this. Much of your ingredient list would be free food, eg meat and veg, and any synned ingredients, eg cornflour, can be found on the syns online section of website.