No, you can't always sub them one for one, unless your particular brand of Stevia happens to be the same strength as most liquid sucralose. For the Sweetzfree brand of liquid sucralose, the concentration is 1 drop = 1 rounded tsp of sugar sweetness. If your liquid Stevia is the same, then you can substitute it one for one, otherwise, I suggest you periodically taste whatever you're making, adding the sweetener a little at a time, until it's sweet enough for your taste.