1/72nd = 0.0138

1/7th = 0.1428 Mulitply your 1/72 measurement by 10.3478

1/8th = 0.1250 Mulitply your 1/72 measurement by 9.0579

You might do just as well by looking (probably in an Architectural supply place) for a scale that already has those ratios on it.

I like to use a spreadsheet, entering whatever measurements I have, then I can change my mind any time about what scale I want to build at, and the spreadsheet automatically does the math. Just set one up, and you can use it as a template for all your scale projects.