TONA and TONAR Refer to the Same Japanese Overnight Rate

Summary

The document resolves a terminology question about Japan’s overnight reference rate. The question contrasts the Bank of Japan’s use of TONA with the TONAR name found in another reference source, and asks whether they identify distinct rates. The accepted answer cites a Japanese bank document describing TONAR, expanded as Tokyo Overnight Average Rate, as the Japanese yen risk-free rate and stating that it is also called TONA.

The practical takeaway is that TONA and TONAR are alternative names for the same rate, rather than separate benchmarks. This is a narrow nomenclature clarification, not an explanation of the rate’s calculation, publication process, market conventions, or use in pricing and trading. The cited confirmation is presented as valid as of the date specified in the source, so readers should consult current official documentation when relying on the terminology operationally.

Key ideas

• TONA and TONAR are alternative names for the same Japanese yen overnight reference rate.
• TONAR expands to Tokyo Overnight Average Rate.
• The source identifies the rate as Japan’s risk-free reference rate.
• The document clarifies terminology but does not explain benchmark calculation or trading conventions.

Tags

# Is there a difference between JPY TONA and JPY TONAR?


# Is there a difference between JPY TONA and JPY TONAR?












Wikipedia defines TONAR as "Tokyo Overnight Average Rate".

The official Bank of Jappan website mentions TONA, rather than TONAR.

I suspect the two, TONAR and TONA, are in fact two terms referring to the same rate, but I just wanted to double check here: hoping for someone knowledgeable of the Japanese market to confirm.

## Answer by Daneel Olivaw (score 5, accepted)

https://quant.stackexchange.com/a/66424

This document [valid as of 2026-01] from Japanese bank Mitsubishi UFJ states they are one and the same rate, see page 3 $-$ my emphasis:

> TONAR (Tokyo Overnight Average Rate), the RFR for JPY also called TONA, is a pre-existing rate.

Shown in full with attribution under the source's licence. Licence: CC BY-SA 4.0 (Stack Exchange)

This summary was written by Stratmill's research agent from the original; it is not a copy of the source.