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Seido Obi Size Chart

Belt Size & Comparative Charts

As an expert in the manufacture of Aikido equipment, Seido is able to provide you with the technical details and measurements of all its models. You will find our elaborate advice on which model to choose after the size tables.

Obi (Belt) Size Table

These measurements correspond to the measurements out of the workshop, not including shrinkage. All measurements are in centimeters, but you can use the unit switcher to switch to imperial system (US).

Belt Size Table

Belt Size 1 2 2.5 3 3.5 4 4.5 5 5.5 6
Belt Length 215 cm 235 cm 245 cm 255 cm 265 cm 275 cm 285 cm 295 cm 305 cm 315 cm
Your waist ~65 cm~ ~75 cm~ ~80 cm~ ~85 cm~ ~90 cm~ ~95 cm~ ~100 cm~ ~105 cm~ ~110 cm~ ~120 cm~

*Length of workshop output. Handmade: 1% margin of error.
*Soft white belt and soft black belt models are 5 cm shorter

How to determine your size

We recommend to measure your belt and make your choice as you like it, but here are some guidance based on what we see the most on the mats. Note that women traditionally tie the obi on their waist and men on their hips.

For Aikido

Check the length of your belt as: length = "waist/hips size" x 2 + 80 cm ~ 90 cm

For Judo

Check the length of your belt as: length = "waist/hips size" x 2 + 90 cm ~ 100 cm

For Karate

Check the length of your belt as: length = "waist/hips size" x 2 + 100 cm ~ 120 cm (120 cm is very long, but it is worn this way in many Karate Dojo)

How to Choose Your Aikido / Judo / Karate Belt

White belts are designed for practitioners before the 1st Dan, color belts are mainly for children, and black belts from 1st dan.

When one buys their first white belt, one chooses whatever is available. Unlike for Judo or Karate, in Aikido, white belt is kept for very long, up to 3, 4, or 5 years. It is therefore more crucial for an Aikidoka to purchase a quality belt that can last for several years.
For this, Seido offers two white belt models. The first is a super soft white belt model, easy to tight, made in Japan. The second model is the "Slim White Belt" entirely made in Japan as well. White belts produced in Japan are extremely rare, and we took great care in developing those high quality models, you will not be disappointed.

Seido black belts are all made in Japan. Our range presents 5 original belts. The soft and slim black belts are made with the same specifications as the corresponding white belts, especially designed to be worn under a Hakama (Aikido). We also offer a reinforced version of the slim white/black belt, a shiny "shushi" cotton black belt and a silk belt, very popular for gift purpose. Those 3 models are still fairly easy to tie, but are closer to the classic Judo belts you can find on the market.

All our belts are composed of a core of 100% cotton, thick or thin, depending on the model.
White and colored belts are particularly flexible, making them easy to tie, and they do not cause discomfort when the practitioner learns to fall.

Finally, the width of the belt, which affects in particular the size of the knot, and the number of seam, which affects its quality and width, are the two key points to consider when making your choice.

Choosing an Iaiobi for Aikido

This kind of obi is typically worn for Iaido practise. As it is tied 3 times around the waste and because of its width it sits very firmly in order to carry a sword. Some Aikido practitioners prefer this type of belt because the knot being flatly tight (or the ends just folded inside the belt) avoids the bulge in front of the centre and allows the Hakama to fall straight. It might also keep the Hakama better in place than an ordinary obi and helps stabilizing the hips. However, this type of belt is not typically used in Aikido and will not hold if it is worn without Hakama. We therefore only recommend it for advanced practitioners.

As all the belts offered by Seido, this belt is also 100% made in Japan. It has a very soft cotton layer on the inside which diminishes the belt's thickness on its entire length, width 6.3 cm, 7 lines of stitching.

Check the length of your belt as: length = "waist/hips size" x 3.5 (+/- ~20 cm, depending on your preferences)"
* Women traditionally tie the obi on their waist and men on their hips.


Soft White Belt model

This model is manufactured in Japan. Outer fabric is 100% bleached cotton. With only 9 lines of stitching and a very soft core, this model is very soft and therefore very comfortable when taking ukemi. Width : 4 cm - 9 lines of stitching.

Slim White Belt model

High quality white belt made ​​in Japan. Outer fabric is made of 100% bleached Japanese cotton. Stiffer than the soft white belt, it has also more lines of stitching. It may be compared to usual black belts in terms of thickness. Width: 4.5 cm - 10 lines of stitching.

Soft Black Belt model

Made from the exact same specs as the white version, this model is very soft and very comfortable. Over time and washes, the belt tends to whiten. Width: 4 cm - 8 lines of stitching.

Slim Black Belt model

With a thickness similar to the Reinforced Slim model, this models presents only 10 lines of stitching allowing to keep extensive softness which result on a tiny knot, useful under the Hakama. Width: 4.5 cm - 10 lines of stitching.

Reinforced Slim Black Belt model

The fabric used for the outer part is identical to the Slim version, however, this model presents 13 lines of stitching, making it stiffer, very close to what's most people consider a "standard thickness" for black belts. Width: 4.5 cm - 13 lines of stitching.

"Shushi" Shiny Black Belt model

Shushi is the Japanese term for a cotton with satin-like shiny finish. A little thicker than other models, this model will tend to whiten over time and washings. Width: 4.5 cm - 15 lines of stitching.

Silk Shiny Black Belt model

Japanese silk is one of the best in the world. With a thickness similar to model C, this belt is made specially to order. A great gift idea! Width: 4.5 cm - 16 lines of stitching.

Seido Budo Belt Comparison

Comparative Table

Thickness/Stiffness Outer fabric Lines of stitching Width Embroidery
Soft White Belt * Japanese bleached cotton 8 lines 4 cm Non-integrated only
Slim White Belt ** Japanese bleached cotton 10 lines 4.5 cm Non-integrated only
Color Belt * Japanese colored cotton 10 lines 4 cm Non-integrated only
Soft Black Belt * Japanese black cotton 9 lines 4 cm Non-integrated only
Slim Black Belt ** Japanese black deluxe cotton 10 lines 4.5 cm Integrated and Non-integrated
Reinforced Slim Black Belt *** Japanese black deluxe cotton 13 lines 4.5 cm Integrated and Non-integrated
Shushi Black Belt **** Japanese black Shushi cotton 15 lines 4.5 cm Integrated and Non-integrated
Pure Silk Black Belt **** Pure Japanese silk 16 lines 4.5 cm Integrated and Non-integrated

About Belt Embroidery

1 - White and Colored Belts

White belts are manufactured and stored in a roll, it is not possible to achieve integrated embroidery (embroidery is done before sewing the belt). Only non-integrated embroideries are possible. They are made within 1 business day

2 - Black Belts

Our black belts are manufactured piece by piece, it is possible to embroider integrated or non-integrated (except for the Soft black belt).
In the case of integrated embroidery, manufacturing time is approximately 3 weeks (made to order and embroidered directly at the workshop during manufacture). In the case of a non-integrated embroidery, and given that our belts are made to order, the shipping time is about 10 days.

Check out our comparative video on Youtube

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