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Footwear

Stack height

What is stack height?

Stack height is how much material sits between your foot and the ground, measured in millimetres at the heel and forefoot. More stack means more cushioning and less ground feel; less means more feedback and a lower, more stable platform.

Stack height at a glance

Low stack
Under about 25 mm
Moderate
About 25 to 32 mm
Maximal
Over about 32 mm

How stack height is measured

Measure from the ground to the bottom of your foot inside the shoe and you get the stack. It's quoted as two numbers, heel and forefoot, because they're almost never the same. A shoe listed as 32/24 has 32 mm under the heel and 24 mm under the forefoot.

Why shoes keep getting taller

The last decade has been a steady march upward. Trail shoes that sat around 20 mm are now routinely in the 30s, driven by ultrarunning, where the accumulated impact of fifty miles makes cushioning worth more than precision. For long days on runnable trail, that's a real gain.

What you trade for the cushioning

What you trade is proprioception and stability. A high stack puts your ankle further from the ground on a platform that can roll, and it filters out the small feedback that tells your foot what it just landed on. On technical, off-camber, rocky ground plenty of experienced runners deliberately choose less stack for that reason.

What this means when you're choosing

  • Stack quoted at both heel and forefoot, which together give you the drop
  • Lower stack if you want ground feel and ankle stability
  • Higher stack for long days on hard ground, if you can live with the height

The common mistake

Assuming more cushioning is always kinder

A tall stack puts your ankle further from the ground, which is more leverage on an awkward rock and less feedback about what you just stepped on. On technical trail that trade can cost you more than the cushioning gives back.

Common questions

Is a higher stack height better for long distances?

For most people on runnable trail, yes, because the cushioning cost of thousands of impacts adds up. On technical ground the stability penalty can outweigh it, so distance alone doesn't decide it.

Is stack height the same as drop?

No. Stack is the total height at each end; drop is the difference between them. A 32/24 shoe and a 24/16 shoe both have 8 mm of drop and feel nothing alike underfoot.

Where this comes up

Guides on Tom's Hiking where stack height changes which product is right for you.

Going deeper

More in footwear

Lug depth

Lugs are the raised blocks on the sole of a boot or trail shoe, and lug depth is how tall they are, usually 3 to 6 mm. Deeper lugs bite into soft ground; shallower ones give more contact area on rock and hard trail.

Outsole

The outsole is the rubber layer on the bottom of a shoe, the part touching the ground. It carries the lug pattern and the rubber compound, which together decide grip, and it's usually the first part of a shoe to wear out visibly.

Midsole

The midsole is the foam layer between the outsole and your foot. It absorbs impact and sets how stiff or soft a shoe feels, and it's the part that quietly dies long before the tread looks worn.

EVA foam

EVA is the light, springy foam most hiking and running midsoles are made of. It cushions well and weighs little, but it compresses permanently over time, which is why shoes go flat after a few hundred miles.

Heel-to-toe drop

Drop is the height difference between a shoe's heel stack and its forefoot stack, given in millimetres. Zero drop means the foot sits level; 8 to 12 mm tilts you forward slightly and shortens the load on the calf and Achilles.

Rock plate

A rock plate is a thin stiff sheet, usually TPU or a nylon composite, embedded in the forefoot of a shoe. It spreads the load from a sharp rock across the whole foot instead of letting it press into one point.

Shank

A shank is a stiffening insert running through the arch of a boot, made of steel, nylon or composite. It controls how much the boot twists and bends, which is what lets a boot support a heavy load and edge on rock.

Rand

A rand is a strip of rubber bonded around the lower edge of a boot's upper, most often at the toe. It takes the abrasion from rock and roots that would otherwise wear through fabric or leather, and it protects your toes from impact.

Gusseted tongue

A gusseted tongue is sewn to the sides of the boot with fabric panels instead of hanging free. It seals the gap along the laces so grit and water can't get in, and it stops the tongue sliding sideways as you walk.

Vibram Megagrip

Megagrip is a Vibram rubber compound formulated for grip on wet and dry rock. It's softer and stickier than standard hiking rubber, which is why it holds on slabs and greasy roots, and why it wears out faster.

Gaiters

Gaiters are fabric sleeves worn over the top of a shoe or boot to keep grit, snow and water out. Low trail gaiters cover the collar and stop scree filling your shoes; tall gaiters run to the knee and seal the leg against deep snow and wet brush.

Microspikes

Microspikes are elastomer harnesses with short chains and spikes, roughly 10 to 15 mm, that stretch over a shoe for traction on packed snow and ice. They are the middle rung between yaktrax-style coils and full crampons, and they are not mountaineering equipment.

Crampon

A crampon is a metal frame carrying 10 or more points up to 5 cm long that binds rigidly to a stiff-soled boot, so a climber can stand on hard alpine ice and steep snow. It is the tier above microspikes, and it is technical equipment that needs an ice axe and training.

Insulation weight in grams

Insulation weight is the mass in grams of one square meter of the insulating sheet inside a boot or glove. A 400g boot uses a heavier sheet than a 200g boot, so it is warmer, but it is nothing like twice as warm.

Vibram Arctic Grip

Arctic Grip is a Vibram outsole technology built for traction on wet ice. It stays pliable at temperatures where ordinary hiking rubber goes hard, which is the reason a winter sole grips where a three season one skates.

Flotation

Flotation is how well a snowshoe keeps you on top of snow instead of sinking into it. It is a function of deck surface area measured against your loaded weight, which is your body plus clothing, boots and everything in your pack.

Heel lift

A heel lift is a small wire or plastic bar behind the heel of a snowshoe that flips up so your boot rests on it during a climb. It stops your calf being held at full stretch on sustained steep ground.

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