Wondering what a men's size 9 in women's shoes actually is? The short answer for most US brands: a men's 9 is roughly a women's 10.5. The longer answer is that shoe size conversion is a convention, not a law of physics, and knowing how the rule works — and where it breaks down — will save you from a closet of almost-right shoes.
This guide explains the standard US men's-to-women's conversion, why width matters just as much as length, how to measure your feet at home, and what to do when a brand only lists one gender's sizing. It applies whether you are shopping across the aisle for a style you like, buying for someone else, or decoding a unisex size chart.
The 1.5-Size Rule, Explained
In US sizing, most brands separate men's and women's scales by about one and a half sizes. To go from a men's size to the equivalent women's size, add 1.5. To go the other way, subtract 1.5. A few quick anchors:
- Men's 7 ≈ Women's 8.5
- Men's 8 ≈ Women's 9.5
- Men's 9 ≈ Women's 10.5
- Men's 10 ≈ Women's 11.5
- Men's 11 ≈ Women's 12.5
The underlying foot length is the same — a men's 9 and a women's 10.5 are usually built on lasts of nearly identical length. The numbers differ purely because the two scales start counting from different points. Some athletic brands use a 1-size offset instead of 1.5, which is exactly why you should never trust the rule blindly. It gets you to the right neighborhood; the brand's own chart gets you to the right house.
Length Is Only Half the Story: Width
Here is the part most conversion charts skip: women's shoes are generally built on narrower lasts than men's shoes of the same length. A man moving into a women's 10.5 may find the toe box and midfoot snug even though the length is perfect. A woman moving into a men's 7.5 may find it roomy through the heel.
Rules of thumb that help:
- If you have wide feet and are converting into women's sizing, consider a wide (W) width or go up another half size.
- If you have narrow feet and are converting into men's sizing, look for styles with adjustable straps or laces so you can snug the fit.
- Stretchy or molded materials — knit uppers, EVA foam, soft jelly-style flats — forgive small width mismatches far better than stiff leather does.
How to Measure Your Feet at Home
Two minutes with paper and a pencil beats any amount of guessing. Stand on a sheet of paper in the socks you plan to wear, trace both feet, and measure the longest distance from heel to toe on each tracing. Use the larger foot — almost everyone has one — and compare that measurement in inches or centimeters against the brand's size chart. Measure in the evening, when feet are at their largest, and re-measure once a year; feet change with age, weight, and activity.
When Conversion Actually Comes Up
Shopping a style made for the other scale
Plenty of shoes are effectively unisex even when they are listed under one gender. Molded comfort shoes are a good example. Okabashi, the American comfort brand, builds its sandals, flip flops, and ballet flats in the USA from soft, recyclable material with what it calls reflexology-inspired insoles and arch support — the kind of forgiving, contoured footbed that fits a wide range of feet once you land on the right length. If a style you want is only listed in women's sizes, the 1.5 rule plus the brand's own chart will get you there.
Family shopping across men's, women's, and kids' scales
Some brands sidestep the confusion by making the same shoe for everyone. Floafers molds its waterproof EVA loafers and slides in men's, women's, and kids' versions of the same silhouettes — the Lane 4 slide, for instance, comes in all three — so each person simply buys their own scale instead of converting. We compared the two brands directly in our Floafers vs Okabashi breakdown if you are weighing them.
Kids' sizes as a bonus conversion
One more trick worth knowing: a US kids' (youth) size runs about 1.5 sizes below the same women's size, so a women's 7 is close to a youth 5.5. Adults with smaller feet sometimes save money in the kids' section, with the same width caveats — youth lasts tend to run narrower still.
Five Mistakes to Avoid
- Trusting the rule over the chart. The 1.5 offset is a default, not a guarantee. Always check the specific brand.
- Ignoring width entirely. Length converts; width does not. Factor it in before you buy.
- Converting European sizes with the US rule. EU sizing is unisex by length — a 42 is a 42 — so no offset applies. Convert your US size to EU first, then shop.
- Assuming athletic and dress brands agree. Offsets and last shapes vary by category. Re-check whenever you switch shoe types.
- Buying tight and hoping. Feet swell during the day. If a converted size feels tight out of the box, it will feel tighter by dinner.
Quick Answers to Common Conversion Questions
Does the rule work in reverse? Yes — subtract 1.5 from a women's size to estimate the men's equivalent. A women's 9 is roughly a men's 7.5.
What about UK sizes? UK men's sizing runs about one size below US men's (a US men's 9 is near a UK 8), and UK women's sizing is roughly two below US women's. When a listing mixes regions, ignore the numbers entirely and match your foot length in centimeters instead — it is the only measurement every chart shares.
Do half sizes matter? More than most people think. A half size is about 4 millimeters of length — small on a ruler, decisive at the toe of a snug flat. If a converted size lands on a half you cannot buy, round up for stiff materials and down for stretchy ones.
Are socks part of the equation? They are. Converting into a snugger women's last while also wearing thick socks doubles the squeeze. Measure your feet wearing the socks the shoes will actually see.
The Bottom Line
A men's 9 in women's is about a 10.5, and the 1.5-size rule covers most US brands most of the time. Measure your feet, respect width, and lean on brands with clear charts and forgiving materials — our roundup of the most comfortable shoe brands and our guide to comfortable slip-on shoes are both good places to start. Get the measurement right once and every future conversion becomes a thirty-second job.