LET me give you a clue – it's not through vaginal sex, oral sex or clitoral stimulation (apparently).
Unsurprisingly men find it easier to reach orgasm than women.
In fact 91% of men reach the big-O while having sex compared to just 64% of women, according to the National Survey of Sex and Behaviour.
Interestingly, men said that their female partners reached climax 85% of the time, which can mean only one thing – they're faking it.
The study – of 1,931 US adults aged 18 to 59 – also quizzed people on the type of sex they were engaging in and noted which ones resulted in orgasm most frequently.
And the results will shock you.
To everyone's amazement anal sex was the most reliable way to make a woman orgasm, with 94% saying they reached the big-O.
Stats-based website FiveThirtyEight has now turned the gob-smacking data into a handy chart, to show the most successful sex acts.
However only 31% of women who took part in the study actually took part in anal sex, so the results may be a bit misleading.
It might also be that people who are willing to try anal sex are more relaxed and adventurous in bed and therefore more likely to orgasm.
The handy chart does also give a rough orgasm guide. Oral sex came in second with more than 80% saying they climaxed when receiving it.
Around 65% said they orgasmed through vaginal sex and mutual masturbation was successful 63% of the time.
The chart also looked into the most reliable ways to make men orgasm – but seeing as they manage 90% of the time anyway the findings were less thrilling.