Probably the best way to do it is vs. images submitted. (so 95 in your example) - and then add up all of the different site's RPI or add up all the sales and divide by 95 for the total RPI.

some people use accepted images at each site - so if a site accepts 50 - that would be the number you use for that site and if another site accepted all 95 you would use that number there.

you certainly wouldn't want to use 258 - as then adding a lower selling site would lower your RPI.

I think RPI can be used as a yardstick, but there are many ways to raise or lower RPI that wouldn't make so much sense if what you really want to maximize is income. (for instance deleting non or low selling images if you use the accepted image # - it doesn't actually raise your income (probably lowers it slightly), but does raise that measure of RPI.

Just did a quick calculation... If I make a RPI of .10 at iStock, I would need 1000 images to make $100.

If I load my 18 images a week at my present 60% acceptance ratio... it would be 93 weeks before I was there....

Dont get too hung up on RPI - I never use it at all myself as I don't think it's useful to YOU, but just means people can compare their portfolios to others.

If I shoot 100 images, and upload them all, but only 10 start to make money, so $10, my RPI is $10/100 = $0.1

but what if I'd only decided to upload 10, and these made $2, then my RPI would be: $2/10 = $0.2 (2 x the RPI)

or, how about I then delete the 90 images that are not selling, then my RPI is $10/10 = $1

NOTE: In every case, you have not taken into account if you are making money or not from this shoot, so for that reason Id rather use ROI for the shoot.

If this shoot costs me $500 in model and prop fees, and I've made $10, then Im still $490 out of pocket. I would monitor these images, to see if (and how fast) I get a return from it. Then I know which shoots are most profitable..

Hope this helps...

To me there are three  key stats - money actually coming in time and cost - If I spend 3hrs fiddling with one image I would want to get more income than one I just do a quick 5mins. Also if I spend money then I want a better return. I don't think RPI is particularly helpful and can produce perverse results as discussed above.