The short answer: nami-sun is standard length, nobi-sun is longer
Kyudo bows come mainly in two length classes: nami-sun (standard) and nobi-sun (longer). In short, the difference is the bow’s overall length. A common guide: nami-sun is about 221 cm, nobi-sun about 227 cm, though exact sizes vary by maker. The keys to choosing:
- The main basis is your draw length (yazuka) — the longer your draw, the more nobi-sun suits you.
- Height is a rough guide — up to about 170 cm, nami-sun; above that, consider nobi-sun (with individual variation).
- Borderline cases: don’t decide by height alone — prioritise draw length and your instructor’s judgement.
What nami-sun and nobi-sun are
Nami-sun is the standard bow (about 221 cm), the most common, and what most beginner class and rental bows are; it suits average builds and non-extreme draws, and its wide availability means more choice in material and strength. Nobi-sun is longer (about 227 cm, roughly 6 cm more); it suits taller people and those with long arms/draw, for whom a nami-sun feels cramped at full draw and puts undue strain on the bow. There are further sizes too — yonsun-nobi (longer than nobi) and sansun-tsumari (shorter than nami, about 212 cm) — but these are less common.
Judging by draw length and height
Draw length
Your yazuka is your draw length at a correct full draw (measured from the centre of the throat to the tip of the left middle finger, with both arms extended to the sides at shoulder height); the arrow itself is ordered longer than this, with a safety margin. The longer your draw, the more length the bow needs, so nobi-sun suits. A standard draw is usually fine on nami-sun. When unsure, look at draw length as well as the height number.
Height (a rough guide)
Roughly: up to about 170 cm → nami-sun; above about 170 cm → consider nobi-sun. But arm length and draw style change the draw at the same height — decide with both height and draw length.
Borderline cases
If you’re around 170 cm: (1) measure your draw accurately; (2) nami-sun if there’s margin, nobi-sun if it’s tight or slightly long; (3) if still unsure, follow your instructor or dealer. A bow is a serious purchase, so have someone watch you draw. For growing students, allow for future growth in height and draw.
Match the arrow length too
The draw length that sets the bow also sets your arrow length: a nobi-sun archer draws longer and needs longer arrows. A long bow with short arrows is dangerous: an arrow shorter than your draw can be pulled inside the bow at full draw. The All Nippon Kyudo Federation (equipment guide, in Japanese) prohibits arrows shorter than one’s yazuka on the target range. Choose bow length and arrow length together.
Getting the length wrong
Too short (nami-sun short for your draw): no margin at full draw, a cramped feel, undue strain on the bow, and less stable arrow flight. Too long (nobi-sun long for your build): the bow feels large and hard to handle, and power is harder to transmit. Length affects not just hits and progress but the life of the bow itself.