Analysing the point gain from thicker arrows

(If you’re just looking for the tool to explore arrow diameter analysis, rather than my very interesting discussion of it just click here)

Without fail, at the start of every indoor season, someone on social medial asks the following question “Why do people shoot thicker arrows indoors?” to which someone else replies “Because the thicker arrows increase your chance of a line-cutter and give you higher scores”. Then follows a debate about whether it actually does or not.

Simple geometry tells us that this must be true – if a thin arrow and a thick arrow land at exactly the same point, the hole created by the thicker one is more likely to cut a nearby line. The more important questions are

1. How big is this effect?
2. Is it big enough to be useful and actually add points to a round?
3. Does this point gain outweigh the disadvantages of shooting and tuning massive tree-trunks?

This article will look at only the first two of those questions – and in doing so will hopefully provide information for archers and their coaches to debate question 3 for their own situation.

Methodology

The key to analysing the point-gain associated with thicker arrows is the UK archery handicap system. This is covered in extensive detail in other articles on this site, such as this page that discusses the mathematical foundations, and this one that discusses how it is used in practice. To summarise though, the handicap system is a well-proven mathematical system for calculating how good an archer is, by modelling their the distributions of group sizes they shoot, and then mapping those distributions on to different target faces at different distances. The end result is a system where performance on different rounds can be compared easily. The handicap of a particular score, or archer, can be used to find a corresponding expected score on a different round. Handicaps sit on a normalised scale between 0 (best) and 150 (worst). For the purposes of some of the charts on this page, I’ll be using negative handicaps too to show areas of performance that are below the systems “scratch point” (1400 on a 90m 1440)

Key to our analysis here is that the handicap equations assume a certain arrow diameter (5.5mm for outdoor rounds and 9.3mm for indoor rounds). We can tweak that parameter to see what effect arrow diameter has on expected score over the range of performance levels. It’s crucial to look at this over a range because the magnitude of the effect will be different – a novice archer that’s scattering arrows all over the target face will not get much benefit from a few more line-cutters, whereas an elite archer whose arrows are teetering on the edge of a scoring zone will do.

Arrow Diameters

Before we start with any analysis, it’s useful to just look briefly at the typical range of arrow diameters used in archery. Depending on where you get your arrows, these may be measured in millimetres or inches. The World Archery rulebook states that the maximum diameter allowed is 9.3mm (0.366 inches), although the point is allowed to be 9.4mm. Typically outdoors people shoot arrows in the 5-6mm range. In some non-WA tournaments, special rules exist, with one of the most notable being the Vegas shoot where larger diameter arrows are allowed up to 0.422 inches (10.7mm). Even though many of the international rules are expressed in millimeters, there is still a strong legacy of using sizes based on 64ths of an inch. The 9.3mm standard is approximately 23/64th of an inch diameter, and the 10.7mm NFAA Vegas maximum diameter is 27/64ths, so people often talk about these as “23s” or “27s”. Here’s a quick conversion chart of a range of diameters.

mm	Inches
4.5	0.177
5	0.197
5.5	0.217
6	0.236
6.5	0.256
7.0	0.276
7.5	0.295
8.0	0.315
8.5	0.335
9.0	0.354
9.1	0.359 (23/64ths)
9.3	0.366
9.99	0.391 (25/64ths)
10.7	0.421 (27/64ths)

Analysis

Let’s start with a simple scenario – let’s say the indoor season has just finished and your heading indoors. You normally shoot a 620 spine A/C/E which has a 0.214 inch (5.44mm) diameter but you’re considering swapping to a max-width 9.3mm arrow for the indoor season. This plot shows the expected point gain along the handicap spectrum. (Note: All of the plots on this page are interactive – you can hover over the line to see the raw data)

This shows that the best case scenario is that you might gain 5.6 points on the round. (To be clear, of course you can’t have 5.6 points, it would be 5 points, but the curves are more informative if you don’t round them, so I won’t for this article). However, that point gain would only be likely for an archer who has a handicap of around 70, which on a WA18 round equates to a score of about 400. To make this chart easier to understand, let’s convert it all into scores, so that now the x-axis shows the thin-arrow score, and the coloured line shows the point gain with the thicker arrow.

In this view we can more easily understand what the analysis is showing – if you normally shoot around 350-500 with the thin arrow, you might gain around 5 points on the round by shooting thicker arrows. After that point the benefit starts to fall off quite quickly. Why – because with so many arrows already in the 10-ring, the opportunity to gain extra points from line-cutters diminishes.

Whilst we’re looking at the WA18 round, we should look at some of its variants

• WA18m round shot on a triple-spot 10-9-8-7-6 face
• WA18m round with compound scoring (which requires the inner-10 ring to be hit to score 10 points)

In this chart we start to see some interesting things –

• The point gain on the triple face is higher, especially in the 80-40 handicap zone. This is because at that point on the performance curve a line-cutter would could be the difference between a 6 and a 5, but on a triple face, it’s the difference between a 6 and a miss.
• At the highest scoring end of the curve for the compound round, there is a spike at showing the tipping point where more of the arrows hit the tiny 2cm inner-10 ring. If you’re a compound archer currently scoring in the 570-580 zone with thin arrows, then moving to a thicker arrow could be worth an extra 6 points.
• As would be expected, the full face and triple-face curves converge at score of 540, which is the point, by definition when all the arrows are scoring on the face, so it doesn’t really matter from that point whether we’re on a full-face or triple-face.

For the sake of mathematical curiosity, we can look at a range of different diameters, against a theoretical 0-diameter arrow –

Vegas – the benefit of an extra 1.4mm

At the Vegas shoot, the normal 9.3mm diameter limit is not used and archers can shoot 10.7 monsters. Let’s take a look at the comparison curve between these two diameters – between a thick and a very-thick arrow.

Here we see the same sort of effect, but much smaller because we’re not comparing thin to thick but to thick and slightly thicker. Looking at the curve, if you’re shooting above 260, the point gain is less than 1. In a statistical sense, that might sometimes mean another point, but practically probably not. For those shooting normally in the 175-250 zone, it might be worth an extra point.

We can see the benfits slightly more clearly by plotting in a different way. Instead of plotting the point gain against baseline score, we can plot the point gain as a percentage of the remaining points. This shows how extra points are more valuable at the highest-scoring end of the spectrum.

What about outdoor rounds?

Whilst this question normally only comes up indoors, we can take a look at some outdoor scenarios too. Here’s a 90m WA1440 round with a thin 4.5mm arrow vs a 9.3mm thick arrow.

Here we see that if you normally shoot around 1000, then you might gain 6 or 7 points by switching up to thick arrows, but I think most would argue that getting a heavy 9.3mm arrow out to those longer distances would cost you many more points in other ways.

On a 70m round it’s a similar story – yes you might gain a couple of points if you’re a 600-700 shooter, but there’s easier ways to gain 2 points that don’t come with the downside of having such a heavy, thick arrow in the air for 70m.

The compound round does again look a bit more practical to gain points from thicker arrows, where it could be worth an extra 4 points over large areas of the spectrum, and even at the higher ends (above 700) it might still be worth another 2-3 points, points which would clearly be valuable at that elite end of a competition.

One further angle to this is looking at the 660 round that was trialled in 2025, which involves 60 arrows on a face where the x-ring scores 11. Here we see a relatively significant point gain potential, with up to 4 points available at the higher ends (600+) of the 70m round and up to 6 points on the 600+ zone of the 50m compound round.

Exploring this topic yourself

If you want to experiment with this type of analysis yourself, maybe to understand if you personally could gain points given your current performance level and arrow setup, you can use the tool included at the bottom of this page, or the standalone version here – ArcheryGeekery’s Arrow Diameter Exploration tool.

Conclusions

Do thicker arrows give higher scores?

• Mathematically speaking, yes, of course, because they’re bigger.
• Practically speaking – it depends. It depends on what sort of score you normally shoot and whether the geometric gain from putting bigger holes in the target outweighs the greater difficulty in getting a heavier arrow to the target accurately and tuning your bow to do so.