Most climbers buy the wrong training edge. Either they go too small too early because it feels more "serious," or they buy a 20mm because someone on Reddit said to and never think about it again. Both miss the point.

The edge you train on isn't a status symbol. It's a tool, and like any tool, it works best when it matches the job. Here's how to actually pick.

Start With Where You Are, Not Where You Want to Be

This is the part nobody wants to hear: you should probably be training on a bigger edge than you think. If you've been climbing for less than a year, you have no business on anything smaller than 20mm. If you're new to structured finger training specifically — even if you've been climbing for a while — 24mm is the right starting point.

At 24mm your full finger pad contacts the hold and your DIP joint (the fingertip joint) sits comfortably on the surface. Nothing is being strained. You're building tendon resilience, learning what progressive loading feels like, and laying the groundwork for everything that comes after. Spend 3–6 months here. It won't feel hard enough. That's exactly how it should feel.

The 20mm Phase Is Longer Than You Think

Twenty millimeters is the universal standard for a reason — it's deep enough for good joint positioning on most hand sizes but shallow enough to build real strength. When coaches prescribe training or researchers measure finger strength, they reference 20mm.

The protocol is simple: hang with added weight, progress slowly. Add 2.5–5 lbs per month. Track your numbers. Rough benchmarks from community data: V4 climbers typically hang around 50% of their body weight on 20mm; V7 climbers around 70%. If you want to know where you stand, we built a calculator for that.

Most climbers who are 2–3 years into training should be spending 6–12 months building max strength on 20mm with progressive weight addition. This is the phase where the real adaptations happen, and leaving it too early is one of the most common mistakes in climbing training. You don't need a smaller edge. You need more weight on the edge you have.

Once you're consistently adding 70%+ of your body weight on 20mm, you've earned the right to think about going smaller.

Going Smaller: 18mm, 16mm, 12mm

18mm is where precision starts to matter. Your DIP joint sits right at the edge, so your finger positioning has to be dialed. A lot of climbers consider this the most useful single edge — shallow enough to be challenging, deep enough to actually load heavy. If you're choosing one edge and you've been training for a couple of years, 18mm is a strong pick.

16mm is advanced territory. The edge no longer supports your first joint comfortably — you're loading the fingertip with real force. Don't go here until your 18mm numbers have genuinely plateaued and you've put in serious time at that depth. Always warm up on bigger edges first.

12mm isn't a progression from 16mm. It's a specialization tool for elite climbers working micro-crimp strength. Training here is about getting comfortable on holds that barely exist. If you're not sure whether you need 12mm work, you don't need it yet.

The Other Direction: Variable-Geometry Edges

Going smaller isn't the only way to progress. There's a different problem worth solving first: on a flat edge, your fingers don't share the load equally.

Your middle and ring fingers reach deeper, make better contact, and absorb more force. Research from Vigouroux et al. (2008) and Fuss & Niegl (2012) measured significantly different force levels at each finger on flat edges. Your strongest fingers get trained hardest. Your weakest ones barely participate.

Variable-geometry edges fix this by changing the surface height across the hold so each finger meets the edge at a different level. All four fingers land in a half-crimp position simultaneously instead of your middle finger doing the heavy lifting while your pinky hangs on for the ride.

The practical result: climbers often hang 10–25% more weight on a variable edge than a flat edge at the same depth (based on our testing and user reports). Not because they suddenly got stronger — because all four fingers are actually working. We wrote a full breakdown of why this happens and who it's for: What Is an Unlevel Edge and Why Use One?

Variable edges are useful for max-recruitment loading phases, for injury rehab, and for anyone whose middle finger pulleys are always the thing that hurts. They don't replace flat edges. They answer a different question.

Hand Size Matters More Than People Admit

A 20mm edge on small hands is not the same experience as a 20mm edge on large hands. Smaller hands make every depth feel a step shallower — 18mm on small hands is closer to the experience of 16mm on average hands. If edges feel disproportionately hard for your climbing level, this might be why. Adjust your expectations and your progression timeline accordingly.

Larger hands have the opposite problem: flat 20mm edges can feel too shallow for comfortable joint positioning, which means you're fighting the hold geometry instead of training your fingers. Variable-geometry edges tend to fit larger hands better because the contouring accommodates the width.

The One Rule

Change one variable at a time. If you're dropping to a smaller edge, go back to bodyweight or light load and rebuild. If you're adding weight, stay on the same edge. Don't shrink the edge and keep the weight — that's how fingers get hurt.

Everyone wants to train on the small edge. The climbers who actually get strong are the ones patient enough to stay on the big one longer than feels cool.