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Brass Instrument Mouthpiece Bore Chart

Listed in order from largest to smallest.

The larger the bore, the bigger and less focused the sound.

Why do the bore sizes increase as the width of the mouthpiece bore decreases? This is the common practice with drill bit gauge sizes — the larger the drill bit, the smaller the number by which it is identified.

#15.7912 mm (0.2280 inches)
#25.6134 mm (0.2210 inches)
#35.4102 mm (0.2130 inches)
#45.3086 mm (0.2090 inches)
#55.2197 mm (0.2055 inches)
#65.1816 mm (0.2040 inches)
#75.1054 mm (0.2010 inches)
#85.0546 mm (0.1990 inches)
#94.9784 mm (0.1960 inches)
#104.9149 mm (0.1935 inches)
#114.8514 mm (0.1910 inches)
#124.8006 mm (0.1890 inches)
#134.6990 mm (0.1850 inches)
#144.6228 mm (0.1820 inches)
#154.5720 mm (0.1800 inches)
#164.4958 mm (0.1770 inches)
#174.3942 mm (0.1730 inches)
#184.3053 mm (0.1695 inches)
#194.2164 mm (0.1660 inches)
#204.0894 mm (0.1610 inches)
#214.0386 mm (0.1590 inches)
#223.9878 mm (0.1570 inches)
#233.9116 mm (0.1540 inches)
#243.8608 mm (0.1520 inches)
#253.7973 mm (0.1496 inches)
#263.7338 mm (0.1470 inches)
#273.6576 mm (0.1440 inches)
Brass Instrument Mouthpiece Bore Sizes

Don’t know which mouthpiece is right for you? Schedule a mouthpiece trial with a professional musician.

5 Responses

  1. Along with playing French Horn, I make jewelry. In seed beads, the bigger the size, the smaller the bead. The explanation is actually more logical in that sizes used to be represented with zeros – 000000 had six beads per inch. When manufacturing processes made the manufacture of very small beads possible, the sizing system had to be updated. So size 15 has 15 beads to the inch. I also work with wire weaving and in wire, the higher the gauge, the smaller the wire. So this all is very logical to me. Anyway, thanks for the chart.

    1. Mr. Groves, great question! We originally included this chart in an article entitled “Anatomy of a Horn Mouthpiece” before we decided it would make a better stand-alone article. But “Anatomy of a Horn Mouthpiece” is in the final editing phase, so check back on our website or on Facebook sometime in the next week for an answer to your question!

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