This Is How Fast Sperm Can Reach the Fallopian Tubes
Studies find it takes 1-5 minutes for sperm to reach the fallopian tubes -- but it's a team effort. Sperm alone only moves about 5mm/min; hormone-driven contractions of the uterus (the myometrium) sweep sperm along and do most of the actual work, growing stronger as ovulation approaches.
No matter how bad your partner's sense of direction is, there's a good chance his sperm knows exactly where to go and gets there fast.
Sperm is fast -- with a lot of help
Several studies find it takes only 1-5 minutes for sperm to reach the fallopian tubes. But that speed isn't sperm swimming alone -- in fluid resembling the reproductive tract, sperm only manages about 5mm per minute on its own, nowhere near fast enough to explain that timeline. Your uterus does the heavy lifting: the myometrium (one of the uterus's muscle layers) contracts, sweeping sperm in the right direction. These contractions are always present, but grow stronger and more frequent as ovulation approaches -- similar to period contractions, except much milder and moving the opposite way (upward instead of downward). You wouldn't even notice them happening.
The hormonal connection
These sperm-transporting contractions are hormonally regulated -- more frequent and stronger during your fertile window than after ovulation, likely because their main job is getting sperm to the fallopian tubes in time.
References
Kunz et al. (1996). Human Reproduction, 11(3), 627–632. Mortimer & Swan (1995). Human Reproduction, 10(12), 3178–3182.
Common questions
Can sperm really swim fast enough to reach the fallopian tubes alone?
Not really -- on its own, sperm moves at about 5mm per minute, which wouldn't get it there in minutes by swimming alone. Uterine contractions do most of the transport work.