Go to running warehouse, find the saucony shoe you want, then click the "shoefitter" button in the description.  It'll ask for the shoe you wear now and what size and stuff.

It's not perfect, but it works much better than guessing.

Dear r/running, I am sure this has been debated somewhere here already, but I had hoped you would still answer me if I posted this.

Anyway, I am using the Asics GT-1000 as my daily trainer and wanted to move to a lower drop shoe. I have found a very cheap pair of the Saucony Fastwitch 5 and purchased a pair based on my Asics shoe's size. 

It turns out the shoes are too small and I have to return them, but I have no way of trying on a pair of Saucony shoes to check out how they fit before exchanging the pair, so I wanted to ask other Asics users, who might've tried Saucony shoes, how much should I upsize compared to Asics if I want the saucony to fit...

A quick question about shoes. Please help...