I was surprised that I could not find a similar (accurate) equation online, so thought maybe others might find this useful. I recently wrote it as part of a mashing spreadsheet for a client. It allows you to calculate target Original Gravity (OG) by plugging in your target A%V and expected Final Gravity (FG). The only equations/calculator I could find used FG and OG to calculate ABV. This equation can be pasted into a spreadsheet; just substitute FG and A%V for the appropriate cells (assuming I typed it correctly here).
I used the following 2 equations from:
Brew by the Numbers by M Hall from Zymurgy Summer 1995
A%V = (A%W)(FG/0.794)