About the math of calculating your knitting progress on triangular shawls

by slowknits

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Take your total numer of rows (in my case 204) and multiply by the total number of stitches at the longest row (471) and you get the total number of stitches your shawl requires.
Total rows = 204
Total sts at last (longest) row = 471
204 * 471 = 96,084
Divide that by 2 and you get the total number of stitches you need to knit to make the shawl.
96,084 / 2 = 48,042

Now take the number of rows you've knitted, say 165, and the number of stitches on the needle, about 385 (I may be off a couple of stitches but you get the idea) and do the same.
Multiply the current row by the current stitches, divide the result by two and you'll get the number of stitches you have knitted so far.

165 * 385 = 63,140 / 2 = 31,570

Now divide the current stitches by the total stitches to get your progress so far:

31,570 / 48,042 = 0.65 (65%)

To put this into a formula where CR = Current rows, Cs = Current stitches, TCs = Total Current stitches, Tr = Total rows, Ts = Total stitches, TOs = Total Overall stitches, P = progress:

(Cr * Cs) / 2 = TCs

(Tr * Ts) / 2 = TOs

TCs / TOs = P