4mm vs 5mm vs 6.5mm Arrows: Which Arrow Diameter Is Best?

4mm vs 5mm vs 6.5mm Arrows: The Quick Answer

Here at Extreme Outfitters, we build arrows in all three of these diameter categories, and there really isn't one that is automatically best for everybody.

If somebody comes into the shop and wants one arrow that can hunt, shoot Total Archery Challenge, practice at distance, and still give us plenty of freedom with the build, I'm usually going to start the conversation around a 5mm shaft.

If somebody is shooting a lot of distance, hunting out west, or they specifically want to reduce how much shaft is exposed to the wind, that's where a 4mm arrow starts to make a lot of sense.

And if somebody wants a simple, proven, affordable hunting arrow and they don't need the advantages of a micro-diameter shaft, there is absolutely nothing wrong with a 6mm or 6.5mm arrow.

What Does Arrow Diameter Actually Change?

The thing you have to understand is that diameter is only one piece of the arrow.

When you reduce the diameter of the shaft, you reduce how much surface area is exposed to the air. That can help in a crosswind, especially as distance gets longer and the arrow spends more time in flight.

The same idea applies after the arrow hits. Once the broadhead has created the wound channel, a smaller shaft has less surface area dragging through the target or animal, so there can be less shaft friction during penetration.

But where people get this wrong is they take that one advantage and assume the smallest shaft must automatically be the best arrow.

That's not how it works.

You still have to look at total arrow weight, spine, GPI, component weight, broadhead design, arrow flight, durability, and the bow you're shooting.

4mm Arrows: Where They Make Sense

A 4mm arrow is the smallest common hunting-arrow category we're talking about here, and this is where you get into what most people would call a true micro-diameter shaft.

For me, the biggest reason to go 4mm is if wind and long-range performance are high on the priority list.

If you're shooting Total Archery Challenge, hunting out west, or practicing at longer distances where you're dealing with wind, having less shaft exposed is a legitimate advantage.

You can also get a benefit during penetration because the smaller shaft has less surface area behind the broadhead.

The Biggest Thing to Watch With 4mm Arrows

The component system matters a lot more.

Because the shaft is so small, you're usually dealing with a HIT-style insert, outsert, half-out, collar, or some combination of those components to get from that small shaft diameter to a standard broadhead.

That doesn't mean 4mm is a bad system. It just means I want to pay more attention to how the front end of the arrow is built.

We want good broadhead alignment, good durability, and a component setup that makes sense for the total arrow weight we're trying to hit.

A good example is the Easton Axis 4mm Match Grade. It gives you that true micro-diameter hunting profile, but you've got to look at the entire component package, not just the shaft itself.

If you're specifically interested in this category, we have a full 4mm arrow guide that goes deeper into the benefits, component systems, and trade-offs.

5mm Arrows: The All-Around Sweet Spot

This is probably where we spend the most time here at the shop.

If somebody wants one arrow that does a lot of things well, a 5mm shaft is hard to beat.

You still get a reduced-diameter shaft, so you pick up some of the wind and penetration advantages, but there are a ton of shaft and component options in this category.

That's what I like about it.

I can take a lower-GPI 5mm shaft and build something lighter and faster for somebody with a shorter draw length or lower poundage. Or I can take a heavier, more durable 5mm shaft and build a hunting arrow that lands much farther up in total weight.

Something like the Easton 5.0 Match Grade gives us a lot of freedom because it's relatively low GPI for a 5mm platform.

The Easton Axis 5mm is more of a traditional hunting workhorse.

And the Victory RIP TKO is another shaft we sell a lot of because it gives you a good mix of durability and build flexibility.

Why I Usually Start With 5mm

For the average compound bowhunter, 5mm just gives us a lot of room to work.

• Plenty of shaft choices
• Plenty of GPI options
• Good insert and HIT systems
• Easy to manipulate total weight and FOC
• Small enough for good long-range performance
• Durable enough for serious hunting use

That's exactly why we use a 5mm shaft as the starting point in our Hybrid Arrow Build.

If you want to compare specific shafts inside this category, check out our guide to the best 5mm hunting arrows.

6mm and 6.5mm Arrows: Still Completely Relevant

One thing I don't like is when people act like a standard-diameter arrow is somehow outdated or automatically inferior.

That's just not true.

A properly spined, properly tuned 6mm or 6.5mm arrow will still shoot extremely well and kill animals just fine.

Where these shafts make a lot of sense is simplicity and value.

The component systems are usually straightforward, field points and inserts are easy to find, and you can build a very good hunting setup without spending a ton of money.

For somebody shooting normal whitetail distances, especially 20, 30, or 40 yards, you may never realistically see enough benefit from going micro-diameter to justify changing your entire setup.

The Easton Sonic 6.0 Match Grade is a good example of a modern reduced-diameter option that still keeps things relatively simple.

And something like the Easton 6.5mm Bowhunter is a straightforward hunting arrow that gives a lot of shooters exactly what they need without making the build complicated.

Diameter Does Not Determine Arrow Weight

This is probably one of the most common misconceptions we see.

People assume a 4mm arrow is automatically light because it's small, a 5mm is somewhere in the middle, and a 6.5mm is heavy.

That's not how it works.

You still have to look at the shaft's GPI — grains per inch.

A 4mm shaft with a thicker wall can weigh more per inch than a lower-GPI 5mm shaft. So if you're trying to build a 430-grain arrow, you have to look at the total weight budget, not just the shaft diameter.

That's why GPI matters so much.

If I want to move more weight to the front of the arrow without making the entire build excessively heavy, I need a shaft that gives me enough room to do that.

You can't look at diameter by itself and know where that finished arrow is going to land.

Does Smaller Diameter Help in the Wind?

Yes, generally.

A smaller shaft gives the wind less surface area to push against, and the farther you're shooting, the more that starts to matter.

That's one of the main reasons we see so many people move toward 4mm and 5mm shafts for western hunting and long-range 3D.

But again, it's not just shaft diameter.

Arrow speed matters. Total weight matters. Vane profile matters. How long the arrow is in the air matters.

So I wouldn't ruin the rest of the arrow build just to get into a smaller shaft.

Does Smaller Diameter Help With Penetration?

It can.

Once the broadhead has created the wound channel, a smaller-diameter shaft has less surface area rubbing through the target or animal behind it.

That can reduce friction and help penetration.

But penetration is one of those topics where people like to isolate one variable and pretend it's the whole answer.

It's not.

We still have to look at:

• Arrow weight
• Momentum
• Broadhead design
• Broadhead sharpness
• Arrow flight
• Impact angle
• FOC
• Component durability
• Shot placement

So I would never tell somebody, "Go from a 5mm to a 4mm and you're automatically going to get better penetration."

Build the whole system correctly.

Is a 4mm Arrow More Durable?

Not automatically.

This is another area where diameter gets too much credit.

Durability comes from the actual construction of the shaft, wall thickness, carbon layup, spine, component system, and how much abuse the arrow is seeing.

We see durability differences inside the same diameter category all the time.

You can have one 5mm shaft that is extremely durable and another 5mm that is noticeably more fragile because it was designed to reduce GPI and preserve speed.

So don't look at diameter and assume you've answered the durability question.

Spine Still Comes Before Diameter

No matter what diameter you choose, you still have to get the spine right.

We see people get this wrong all the time.

Draw length matters. Draw weight matters. Arrow length matters. Front-end weight matters.

If you start adding point weight or heavier components up front, you're dynamically weakening the arrow. If you cut the shaft shorter, you're stiffening it.

A perfectly chosen diameter with the wrong spine is still the wrong arrow.

If you need help understanding that side of the build, read our guide to choosing the right arrow for your bow.

So Which Diameter Should You Choose?

Go 4mm If...

You're shooting a lot of distance, dealing with wind, hunting in open country, or you specifically want the smallest shaft profile you can reasonably build around.

Just make sure you're paying attention to the component system and not choosing it just because smaller must be better.

Go 5mm If...

You want the most balanced option.

For most compound bowhunters, this is where I personally like to start because we have so much freedom with shaft weight, components, FOC and overall durability.

Go 6mm or 6.5mm If...

You want something simple, proven and affordable, and your hunting or shooting doesn't require the advantages of a micro-diameter shaft.

For a lot of whitetail hunters shooting normal distances, that's still a perfectly good answer.

Bottom Line

The best arrow diameter is the one that lets you build the complete arrow correctly for your bow and what you're trying to do.

A 4mm isn't automatically faster. A 5mm isn't automatically perfect. A 6.5mm isn't outdated.

For most compound bowhunters, I like the balance of a 5mm shaft. If wind and long-range shooting are a bigger priority, a 4mm deserves a hard look. If simplicity and value matter more, a 6mm or 6.5mm setup can still be an excellent hunting arrow.

Whatever you choose, start with the right spine, decide what you need the arrow to do, and build the entire system around that instead of chasing one number.

You can also use our FOC Calculator and Kinetic Energy Calculator when you're working through your next build.