Okay, I know everyone is shaped different and it is totally just an estimate BUT I ordered a bunch of new tops in size 18. Looks like it should have been size 20. They fit, but are pretty snug (feel fine, but show every bump). I'm torn - if I send them back and re-order in size 20, how long will I be able to wear them? But if I hang onto them, how long will I have to wait until they fit? I'm 5'6" and 217 pounds, with 52" hips and 42" waist (and why the heck do catalogue sizing charts never seem accurate?? Geez - I'm wearing size 20 jeans and I'm usuall a size smaller on top) - anyone with similar dimensions have advice?

Here's my chart which assumes a human can be modeled as a spheroid but includes a tuned power scale factor of 0.64:

Waist Height Volume % Scale Factor Weight
51 70 762653.0326 100% 296
50 70 733038.2858 97% 288.5914706
49 70 704009.9697 95% 281.2243153
48 70 675568.0842 93% 273.8991405
47 70 647712.6294 90% 266.6165742
46 70 620443.6051 88% 259.3772672
45 70 593761.0115 85% 252.1818947
44 70 567664.8486 83% 245.0311575
43 70 542155.1162 80% 237.9257839
42 70 517231.8145 78% 230.866531
41 70 492894.9434 76% 223.8541872
40 70 469144.5029 73% 216.8895734
39 70 445980.4931 71% 209.973546
38 70 423402.9139 69% 203.106999

YMMV

Using your numbers but my scale factor, I get:

Waist Height Volume % Scale Factor Weight
52 66 747548.2551 100% 217
51 66 719072.8593 98% 211.6729095
50 66 691150.3838 95% 206.3749873
49 66 663780.8286 93% 201.1066522
48 66 636964.1937 90% 195.8683378
47 66 610700.4791 88% 190.6604932
46 66 584989.6848 85% 185.4835838
45 66 559831.8109 83% 180.3380925
44 66 535226.8572 81% 175.2245204
43 66 511174.8239 78% 170.1433883
42 66 487675.7108 76% 165.0952376
41 66 464729.5181 74% 160.0806321
40 66 442336.2456 71% 155.100159
39 66 420495.8935 69% 150.1544304
38 66 399208.4617 67% 145.2440859
37 66 378473.9502 65% 140.3697934
36 66 358292.359 62% 135.5322521
35 66 338663.6881 60% 130.7321943
34 66 319587.9375 58% 125.9703882

Take it for what it is worth

From the way my body has been it can be 10-20 pounds depending on how snug is okay to wear them.

Does that make sense?

It is typically for me 15 pounds to the next size.

Thank you both - that scientific equation is amazing! And both answers show about the same range, so I think I can expect it to fall in there :-)

Yes, I agree. I found that at about every 15-20 lbs of loss, before I went into Onederland, I changed size.

Below 200, that shifted for me to about every 10 lbs of loss.

At your current weight, have you thought about hitting Goodwill to get you through until you get to your goal? It can be a huge money saver.

Well, first let me say yes it does look pretty cool. Unfortunately the precision is misleading and I think you've got the right take. It's somewhere around two inches for every 13 pounds... +/- a few pounds.