Use the online Ikea bathroom planner. Fast, easy, and to scale.

Oh thank you for that suggestion!

When I was planning my bathroom someone pointed out not wanting to have the toilet right there as you step out of the shower and that opened my eyes to a whole new perspective of what we might do instead. Also, depending on how straight your walls end up being and whether any of it needs to be built out for tile, your shower + tub wall may not end up with your exact dimensions so be careful that it all can fit. Toilet seems to be taking center stage in this layout in that it's right there as you walk in, right there as you get out of shower and right behind you if the vanity is going to be on the wall opposite shower/tub.

Thanks for the input Gabriel. This is the layout for the current bathroom. We are trying to decide where to put everything once we gut it. The current shower is pretty small. We need to keep the tub though.

It will be less expensive to keep the current plumbing and drains where they are. If you have to rearrange the tub, shower and toilet, you have to change the drain pipes I think. Check your codes in your area.
We were able to use the same layout, get a smaller tub and slightly enlarge our shower stall and it all fit great. It was still a complete gut job, but I was advised not to get rid of the tub and close up the window by tub to save costs.