Taking a pattern and making a bigger size with it

Does anyone out there have any nice math formulas or calculators to take a pattern and figure it out for a bigger size? I found a pattern that I am using to make some sundresses for my daughters, but the pattern only goes to a size 4 which is fine for my 3 year old. However I would like to make a matching dress for my 7 year old. How can I take the pattern and figure it out for a size 8?

Any tips would be appreciated! :shrug:

There are bunch of links to gauge converters. Try a search using the forum search tool (at top of page). Put in gauge converter (or calculator).

Thank you - I just needed to know the correct term to search better.
Appreciate the help!