Happy almost-weekend FlyerTalk!
The consulting business is a bit slow in the summer, so I spent some time recently writing a tool to calculate RDMs, MQMs, MQDs, and which lounges you have access to based on your itinerary, Medallion status, and relevant credit cards. I have always been comfortable doing the math with the great circle mapper and the earning tables for partner-marketed flights, but writing a calculator seemed like a fun project, and might be able to get people quick answers to things like partner MQDs and lounge access when they ask.
The website is at
www.qualifyingmiles.com, and I would appreciate any feedback FlyerTalk has to offer.

This is interesting, but a couple of observations based on my recent domestic trip (this week).
PDX-ATL-GPT-ATL-PDX
Your tool calculates PDX-ATL at 2169 miles, but it has been 2172 for the eight years I have been flying it regularly. Small difference, but it could add up.
I *think* Sky Club access is only considering departure airport? The calculator claims that I won't have lounge access on GPT to ATL flight
The MQD calculation seems to be discarding decimal places when you enter the exact ticket cost. In my case, my ticket was $775.24 excluding taxes. If I enter whole numbers, $774 calculates 774 MQD. $775 also calculates 774 MQD. $776 correctly figures 776. Delta always rounds up. After some further playing around with it, it seems like you might be doing your rounding on the result of your calculations instead of on the input number. This is creating some really weird results.
For example, on my ticket, entering any price between 775.00 and 775.24 results in 774 MQD. Any price between 775.25 and 777.56 calculated 776 MQD.
This happens with other values, too. For example, entering a price between $98.80 and $101.11 comes up with $100 even
I think that if you rounded up first, and then just used that number for the MQD total you would be more accurate. When I have multiple segments and the MQD is an odd number, Delta seems to just subtract 1 or 2 MQD from one of the legs. I know it's extra math, but doesn't seem insurmountable.
Here are the actual earnings from this recent trip (I'm DM, so RDM is 11x):
PDX-ATL - 2172 MQM - $334 MQD - 3674 RDM
ATL-GPT - 500 MQM - $55 MQD - 605 RDM
GPT-ATL - 500 MQM - $55 MQD - 605 RDM
ATL-PDX - 2172 MQM - $332 MQD - 3652 RDM
Totals - 5344 MQM - $776 MQD - 8536 RDM
Hope some of that is helpful.