When I started PE, I did some heavy research to determine average penis dimensions and "the women's ideal" dimensions, so I could chart my measurements and gains against an "average" and "ideal." I do medical research for a living, so have access to even the raw data (key to understanding the average) and method details from most published studies. As you could guess, there is alot of variation between different studies - not just measurements, but also study methodology. So, take averages with a grain of salt as variance of raw data can be high. I sifted through the data from what I considered credible studies and cleaned it up to come up with my own set of measurements for what women consider ideal. Here are the numbers I use - 6.9" BPEL and 5.1" EG, which has a volume of 234ml, depending on penis geometry. I did adjust the data best I could to account for the BP vs NBP issue. Don't ask me to cite all the studies, because I didn't keep a list - sorry.
One thing to keep in mind is that women, understandably, give a different answer when asked for ideal size for a regular partner and ideal size for a one-night stand/optimal orgasm. Most go for a significantly larger penis for a one-night stand, especially larger girth (over 5” EG). The average I stated is a blend of these sizes. There was a clear preference (far less data variance) for more girth as opposed to more length in both preference for regular and one-nighter sizes. I found in the data that if women had to choose between average length and big girth or longer length and average girth, they strongly tend toward taking the larger girth option. I also noted a clustering of women who liked a MUCH larger girth for optimal orgasm. But that cluster had a pretty clear “max” at approaching 6” EG.
Another thing to keep in mind when looking at studies is that both women and men are terrible at guessing length or girth sizes. When women are asked to just state a size preference, like in an online survey, they invariably state a much longer size (8” length preference came up in a recent study). BUT, in studies when women are actually allowed to see and hold a model of a penis (like a dildo), they invariably choose a much shorter model as ideal (6.5-7.0”) and often guess its length as much longer than it actually is. What is more consistent in both methods is the preference for girth over length. You can also find loads of posts by women saying how surprised they were when they measured their “hung” guy only to find out they weren’t anywhere near 8” after all.