New Balance 665 Sizing Guide: True to Size? (51 Pairs)

New Balance 665 Sizing — What 51 Pairs in the Feetlot Database Tell Us

The New Balance 665 is a budget cross-trainer in the Feetlot database, with 51 owner-reported pairs logged so far. Across those owners the fit pattern points clearly at true to size: the average wearer takes the same number they wear in a standard lifestyle sneaker. The sample is smaller than the headline silhouettes, so the recommendation is directional rather than locked-in, but it lines up with how New Balance's mainstream training and walking lasts tend to fit.

The 665 uses a roomier walking-style last with a mesh and synthetic-leather upper, which is why it lands true to size instead of running tight. The bigger story with New Balance is width, not length: the 665 is offered in standard (D) plus wider fittings, so wide-footed wearers have a real width option instead of guessing with the length number.

Should You Size Up or Down in New Balance 665?

Standard fit (most people)

Stay true to size. The 665's last is forgiving through the toe box and the cushioned collar holds the heel without needing a size adjustment. According to Feetlot data, the typical 665 wearer buys the same number they wear in everyday sneakers and gets a comfortable, secure fit straight away.

Wide feet

Stay true to size in length and choose a wide width instead of sizing up. New Balance is one of the few brands that builds the 665 in wider fittings, so wide-footed wearers get the extra room across the forefoot without lengthening the shoe and letting the heel slip. Going up a full size to chase width usually leaves the foot sliding forward.

Narrow feet

Going down half a size works for genuinely narrow feet who want a tighter hold around the midfoot and heel. The synthetic upper does not compress to a narrow foot the way a knit would, so half a size down is the maximum — a full size down leaves the toes cramped, and the shoe will not stretch in length to fix it.

New Balance 665 width options

Length sizing stays the same across width fittings — a D-width 10 and a wide 10 are the same length, just different volume across the forefoot and instep. Pick your width by foot shape, not by changing the size number. Most wearers stay true to size regardless of the width they buy.

How New Balance 665 Compares to Other Sneakers

The New Balance 665 sits very close in length to most lifestyle sneakers. According to Feetlot data, the 665 fits at essentially the same numerical size as the Nike Air Force 1, Air Jordan 1, Vans Authentic, Air Max 90, Blazer Mid '77, Air Jordan 4, adidas Superstar, Nike SB Dunk Low, and Air Max 97. If a wearer takes size 10 in any of those, they take size 10 in the 665 too.

The exceptions where the numerical size shifts are small. The adidas YEEZY Boost 350 V2 runs about half a size smaller-fitting than the 665, so take half a size up in the YEEZY compared to your 665 number. In the other direction, the Converse Chuck Taylor and boot-style models like the Clarks Desert Boot run about half a size larger, so go half a size down from your 665 number when buying those.

Sign in to Feetlot and add a few of your other sneakers to get a personalized New Balance 665 size recommendation calibrated to your actual foot rather than to the population average.

New Balance 665 Size Chart (US / EU / UK)

Common Sizing Mistakes

• Sizing up for width. The 665 comes in wide fittings — buy the wide width at your true length instead of going up a full size, which only adds slack the shoe can't tighten back up.
• Treating it like a tight Nike runner. The 665 fits true to size, not snug. Don't size down out of habit just because some performance runners need it; only narrow feet should drop half a size.
• Buying small expecting stretch. The mesh and synthetic upper softens slightly but does not grow in length. A 665 that's too short stays too short.
• Assuming women's and men's numbers match. A US women's size runs about 1.5 larger than the men's number — a women's 11.5 is a men's 10. Convert before you order.
• Copying a YEEZY or boot size straight across. The 665 runs half a size different from YEEZY 350 V2 and from boots like the Clarks Desert Boot, so adjust rather than reusing that number directly.

How Feetlot Computes These Numbers

Every New Balance 665 sizing recommendation on Feetlot is the output of a global offset model fit to over 100,000 owner-reported shoe records. Each shoe gets a single number — its "size offset" — that captures how much its sizing drifts from the reference shoe (the Nike Air Force 1). When a Feetlot user provides their size in any tracked sneaker, the model recovers their true foot baseline and recommends the matching 665 size.

This works better than the more common pairwise approach because Feetlot uses the entire wardrobe graph. A YEEZY 350 owner contributes data about how YEEZY fits relative to Air Force 1 owners, which links to owners of the 665 (many of whom own a mainstream sneaker too), and so on. Even when two users share zero shoes directly, the chain of users in between transmits a consistent recommendation. The result: sizing advice that holds up no matter how unusual a wardrobe is.