Measuring arch height for insoles starts with the wet foot test — dip your foot, step onto cardboard or a paper bag, and compare the footprint to a four-category arch height chart to pick Low, Medium, High, or Extra High support.
A wrong arch height turns a supportive insole into a footache. Getting it right takes thirty seconds and nothing you don’t already own. Here’s how to read your own footprint and pick the insole that fits.
How The Wet Foot Test Works
The wet footprint method is the industry standard across Currex, PowerStep, TreadLabs, and Superfeet. It classifies feet into four arch heights based on how much of your midfoot leaves a mark when you stand normally.
What You Need
- A shallow pan, bathtub, or shower floor with a thin layer of water
- A surface that holds a clear imprint — flattened shopping bag, cardboard, or thick paper
- A towel to dry off
The Steps
- Dip one foot so the entire sole is wet. Superfeet confirms the test works with or without socks.
- Step carefully onto the surface you prepared. Transfer your full standing weight onto that foot.
- Step off and look at the imprint. Do the same with your other foot — arch height can differ between left and right.
- Compare each footprint to the arch height chart below.
PowerStep defines the high-arch mark as a footprint where the ball of the foot and heel connect by a thin line and the arch is clearly raised off the ground. TreadLabs goes further, splitting high arches into High and Extra High — if your midfoot barely touches the surface at all, you’re in the Extra High category.
Arch Height Classification
| What Your Footprint Looks Like | Arch Height | Best Insole for This Arch |
|---|---|---|
| Entire sole visible when standing and sitting; no gap | Low (Flat) | Low arch support with firm heel cradle |
| Flat when standing, but arch appears when you sit; a thin line connects heel and ball | Medium (Normal) | Medium arch support with moderate contour |
| Arch is raised off the ground when standing; ball and heel connected by a thin strip | Medium | Medium arch support |
| Midfoot touches the ground very little; imprint looks like two separate pieces | High | High arch support with deep metatarsal pad |
| Midfoot barely touches at all; two distinct blobs with a wide gap | Extra High | Extra High arch support; may need custom orthotics |
The Pencil Test — Superfeet’s Quick Check
Superfeet created a second method that takes about ten seconds. Grab a pencil with an eraser on the end. Plant your foot flat on the floor with your full weight on it. Point the eraser at your arch and slide the pencil underneath the highest point.
- The pencil stops at the eraser — Low Arch.
- The ferrule (the silver band under the eraser) fits under the arch — Medium Arch.
- The pencil slides past the ferrule — High Arch.
This check is less precise than the wet footprint, but it works as a fast sanity check when you’re between two categories.
Common Mistakes That Lead To Wrong Insoles
Weighting vs. Unweighting Confusion
If your feet look flat when you stand but show an arch when you sit, you have Medium arches, not Low ones. Picking Low insoles for this foot type leaves you under-supported and still uncomfortable.
Ignoring the Second Foot
Currex warns that one foot may be a half-size different in arch height from the other. Test both feet and buy for the higher arch — you can always add a very thin shim under the lower arch’s insole.
Thin Paper That Shows Nothing
A piece of printer paper won’t hold a readable imprint. Use cardboard, a paper shopping bag, or thick art paper. If the outline is fuzzy, the test fails.
Flexible vs. Rigid Feet
TreadLabs notes that flexible feet — ones where the arch appears when you curl your toes upward — often pair best with Medium support even if the footprint looks High. A rigid low arch should never take a High insole; the “golf ball” sensation under the midfoot is a sign you’ve over-corrected.
Getting Measured Professionally
Red Wing stores in the US offer free foot scanning using specialized equipment. The scan generates an emailed report that lists your exact length, width, arch height, heel width, and instep measurements. This is the most precise option for matching insoles to your foot’s geometry, but it requires a store visit. If you can get to a Red Wing, it’s worth the trip — especially if the home tests feel ambiguous.
Once you know your arch height, browse our roundup of the best arch support insoles for boots to match your measurement to the right pair.
Safety & Fit Guidelines
| What Can Go Wrong | Why It Happens | The Fix |
|---|---|---|
| High arch insole on flat feet | Over-support pushes the arch uncomfortably high | Use Low arch insoles only |
| Extra High arch on medium feet | Too much support causes instability and fatigue | Match your measured height exactly |
| Insole bends in half with your hands | Shoe lacks a rigid shank; support collapses | Only use these insoles in boots with a stiff shank |
| Heel pocket compresses when squeezed | Shoe lacks a rigid heel counter; insole shifts | Boots with firm heel counters are required |
| Severe plantar fasciitis or foot pain | Home tests can’t detect underlying conditions | Consult a podiatrist before buying insoles |
Dr. Scholl’s and Gotham Footcare both advise that anyone with diabetic foot issues, arthritis, or chronic arch pain should see a medical professional — the wet test measures geometry, not pathology, and a collapsed arch can look like a High arch on paper while needing very different support.
The Complete Selection Checklist
You now have the measurement. Here’s the sequence that lets you make a confident buy.
- Run the wet footprint test on both feet.
- Check each foot against the arch height chart. If the two differ, buy for the higher arch.
- Run the pencil test as a tiebreaker if you’re between two categories.
- Make sure your boot has a rigid shank (doesn’t bend in half) and a firm heel counter (doesn’t compress when squeezed). Without both, no insole works right.
- Match your measured arch height to the correct product — Low, Medium, High, or Extra High.
If you stand in one spot for more than a minute in the right insole and feel relief instead of a new ache, you got it right.
FAQs
Can I measure arch height without getting my feet wet?
Yes — the pencil test from Superfeet works dry and takes about ten seconds. Slide a pencil under the highest point of your arch while standing; where the pencil stops tells you Low, Medium, or High. It’s less precise than the wet footprint but provides a fast second opinion.
Do I need to test both feet separately?
Yes. Currex and PowerStep both emphasize that arch height can differ between feet. One foot may need Medium arch support while the other needs High. Always test both and buy for the foot with the higher arch, adding shims under the lower arch’s insole if needed.
What arch height should I pick if my footprint looks different standing vs. sitting?
Choose Medium. If your foot flattens completely under weight but shows an arch when you sit, you have flexible medium arches. Low insoles would under-support you, and High insoles would feel like a golf ball under your midfoot.
How do I know if my boots are stiff enough for aftermarket insoles?
Grab the boot by the heel and toe and try to bend it in half. If it flexes easily, the shank is too soft and the insole won’t stay positioned correctly. Then squeeze the heel counter — if it compresses like fabric, the insole will shift inside the boot.
What if the home test and the pencil test give different results?
Trust the wet footprint as your primary result. The pencil test is a quicker and less reliable method. If they disagree by one category, use your comfort instinct — whichever feels better during a five-minute wear test in the store is your answer.
References & Sources
- Superfeet. “How to choose the right insole arch height for your feet.” Describes the pencil test and eraser/ferrule metric for arch height selection.
- Currex. “Fitting at Home.” Defines the wet test as the simplest home method for measuring arch height.
- PowerStep. “Finding Your Arch Height.” Provides wet test steps and a clear definition of high arches.
- TreadLabs. “Arch Height Chart.” Quantifies four arch categories from Low to Extra High with footprint examples.
- TreadLabs. “Arch Height 101: How to Tell if You Have High Arches.” Covers flexible vs. rigid feet and the toe-raise test.