Swim Fin Sizing Made Easy!

Swimming with fins is an important way to develop your kick and build leg strength.

Read this guide and learn how to get the perfect fit, every time.

Proper Swim Fin Sizing Is Easy

Can selecting your swimming fin size be as straightforward as checking your shoe size?

Not always, but fitting fins shouldn’t be challenging or frustrating.

5 Key Tips For Fitting Fins

Sole To Sole Swim Fin Comparison
Match sole to sole to assess fit.

1. Shoe Size

Start by choosing fin size based on your shoe size. If you wear a size 10 in your daily shoes, begin with a size 10 swimming fin.

Upon receiving your fins, or during your visit to a Kiefer Swim Shop, make a visual comparison by aligning the sole of your shoe with the sole of your fin.

2. Trying On Your Swimming Fins – Dry / Wet


Toe Position

It’s OK for toes to show in the fin’s foot pocket window, but make sure that your toes do not protrude from the foot pocket window.

Dry Fitting – Be Careful!

If you are fitting fins dry, inserting your feet into the swim fin foot pocket is met with ample resistance. Some new fins are “greased” or “powdered” and may not present this issue, but most swimming fins are not.

Swim Fin Fitting
Don’t allow a loose fit! Fins should be snug.

Struggling to enter dry fins may cause you to “size up” unnecessarily, resulting in floppy fins that are inappropriately loose in water.

Wet Fitting – Ideal!

The ultimate approach to fitting swim fins is fitting them in the water and taking them for a spin in the pool.

3. Close, Snug Fitting Swim Fins Preferred!

Fins should fit snugly; if you can fit multiple fingers in the space between fin and skin they are too big. Fins should not be loose. A loose fin will cause chaffing and likely painful blisters in the long run.

4. Between Fin Sizes? Put A Sock In It!

Kiefer Lycra Watersox
Add Kiefer Lycra Watersox to fill unnecessary gaps.

If you find that your feet fall between fin sizes, don’t give up! Grab Kiefer Lycra Socks to fill the gaps. They will add padding and comfort and eliminate uncomfortable rubbing.

5. Not Satisfied With The Fit Of Your Fins? Don’t Worry!

We want swimmers to be happy with the fit of their Kiefer Swim Fins.

Save your receipt! If you are unhappy with the fit of your fins, follow Kiefer’s Returns procedure to exchange/refund fins fit in the water that do not meet your fit expectations.

Kiefer Can Fit You!

There is a good fit for everyone out there. Don’t let one bad fit get you down – try our selection of swim fins to discover what works the best for you and your swim training.

Looking for help choosing a swim fin style? Check out our blog post on how to choose swim fins.

Learn More About Swim Gear: 

About Emily Milak

Emily Milak is a lifetime competitive swimmer living in Southeastern Wisconsin. Emily is a US National Team champion, NCAA champion, and USMS champion with extensive coaching experience. She is a product development consultant at Kiefer.

14 Comments on “Swim Fin Sizing Made Easy!”

  1. I’m looking for fins to use in rehabilitation from Ankle Surgery.

    Length of feet 11 1/4 inches long. Width of feet 4 1/2 inches wide. Height of feet at the 4 1/2 inch point – one and ahalf inch thick.

    Prefer closed heel, And a relatively flexible fin rather than a stiff fin.

    Silicone could be the best, for flexibility Around the foot.
    Thank you,
    Ed Maurina
    Ed [email protected]

    • Hello Ed! You can use your shoe size to help you fit a fin, they aren’t as precise but you can get pretty close. If you feel like you are between sizes, you can size up and wear a neoprene sock, or a regular one if that works for you. We carry Lycra water socks to help fill any gaps as well. Our Kiefer Silicone Training fins do have a closed heel if that is your preferred material and they are available in men’s sizes 4-15 and women’s 6-13. Hope that helps!

  2. I am buying on line. Want to see if snorkeling is for me without spending a lot. The sizing described in the ads don’t seem to relate to shoe sizes. If it says size 3-5 but doesn’t say “kids” what shoe size is it? Sometimes it says adult size medium 7 to 10. Would my size 9, 91/2 shoe size match with that size? Thanks

    • Yes your 9 to 9.5 would fit in the adult medium 7 to 10 size! But if you are able to find a vendor or attend a swimming event you might be able to try a few on in person to be 100% confident about fit. If you end up with something too big you can wear socks or get neoprene snorkeling socks as well.

  3. Hi – I am finding it very difficult to find a short swim fin to fit my daughters very narrow foot! Do you have any recommendations? She is a size UK 2

  4. I’m 82 yrs old in good health. I used to swim a lot until I had an unrelated shoulder injury. I was a casual swimmer. I would like to get back to swimming but my legs seem weak. I do water aerobics and walk the lazy riber

    • Hello Janet! I’m sorry to hear about your shoulder injury. It sounds like you are doing the right things to build strength in your legs with water aerobics and walking in the lazy river, keep at it! Sometimes its easy to feel like progress isn’t being made because it isn’t happening as fast as you’d like. If you’d like to get back to lap swimming, perhaps try a pair of fins to help your legs along. They will increase your workload and make you swim a little faster. In regards to your shoulder injury, I suggest no kick board. Kick on your back with your hands at your side, or on your side with one arm up, to rest your head on, and one at your side resting on your hip. Best of luck recovering!

    • Hi Jane, looks like the closest we’ve got is youth 11-1 which is the green thrust fin. Little ones are a bit more challenging to fit, there isn’t much out there for them at this age. I’m finding the same problem looking for a pair for my four year old as well.

      In the past I have found adjustable snap fins from Finis, however that was some five or six years ago now.

    • Hi Richard, it looks like our fins as well as a few of our competitors fin sizes kind of stall out at the 13-15 range. Our Kiefer rubber fins do have some flex to them for sure, but without fitting you in person I couldn’t say with certainty that they would be comfortable. One thing that might help with tight fins are a pair of socks, which of course would make them more snug, but it would help alleviate friction between the fin and your skin.

  5. I have size 9 shoes. Why isn’t their a small-xl chart that shows what size fins = size 9 feet?

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