Format 720kb IBM floppies to 880kb Amiga format?

[Lord Aga]

DD floppies are 1MB, HD 2MB (in raw capacity, theoretically so to say). Different computers have different efficiency when formatting.
PCs format them at 720KB. Amiga  at 880KB.
I'm not quite sure what are you trying to do ?
If you insert a DD floppy in your Amiga, and format it, it will have 880KB free space. And you can write ADFs on it.

[Lord Aga]

I have a whole bunch of big-box IBM/Tandy games that I'd like to convert to their respective Amiga releases.

That's a good plan
Just go for it. There are no PC and Amiga disks. Just DD floppies. Put them in your Amiga and format them at 880K. A good recipe to enjoy the holidays

[Lord Aga]

Yes, I use floppies under W7.
Had to format them on Amiga though.