What are folks using to calculate YTD and monthly gain/loss?
Just recording values at the beginning and end of each period?
Well that, plus I take into account any additions or withdrawals during the period.
So, if I had $1M on 12/29/23, and $1.1M on 1/31/24, but put in an extra $100K in that month, my return would be zero, and not 10%.
Now I'll admit, my formula for calculating the return isn't perfect. I don't know the truly proper way to do it. So, I calculate it pretending the net withdrawals/deposits were all done at once, at the beginning of the period, and then again at the end of the period, and take the average of the two.
So, if I had $1M at the beginning of the period, $1.1M at the end of the period, but over that period, put in an extra $50K total, I'd calculate it as:
$1.1M / ($1M + $50K), and then ($1.1M - $50K) / $1M, and take the average of the two.
In this case, that comes out to 4.76% and 5.00% respectively, with the average being 4.88%, and that's the number I would quote.
I've already updated my numbers to reflect February 1, so my formula has lost the 1/31 numbers. However, as of 2/1, the two numbers are 1.93% and 1.94%, respectively. I haven't added enough to my investments, to really make any meaningful difference at this point in the year.