Byo-yomi clocks: the hardware, and what a phone does differently
A byo-yomi clock is a two-sided game clock that can run japanese byo-yomi periods, not just count down. Very few devices are built for it: the one that turns up in shop after shop is the DGT 1005, listed in every country literally as the "Byo-yomi Timer", offered around US$35 / €30. In Japan the category is its own product class: Japanese Go and shogi shops stock the Citizen The Meijin-sen DIT-50 and the Seiko BZ361L, at roughly ¥16,000 and ¥8,000. Everything else on the shelf is a chess clock that may or may not have a byo-yomi mode hidden in its presets. This page compares the two ways of getting a real byo-yomi countdown — a dedicated device, or the phone already in your pocket — and says plainly where each one wins.
What is actually on sale
These are devices found on Google Shopping and Amazon in August 2026. Prices move, sellers differ per country, and none of these links are affiliate links — the list is here so you can judge the market, not so we can sell you something.
| Device | Observed price | Where it turns up |
|---|---|---|
| DGT 1005 — sold as "Byo-yomi Timer" | US$35 · €29.95 | Librium Games, Schachversand, the German Go shop go-spiele.de |
| DGT 2500 (sold as a Go/chess clock) | €66 | Hebsacker Verlag |
| DGT 2010 (FIDE chess clock) | US$74.99 | Amazon |
| DGT 1001 | US$29.99 | Newegg |
| ZMF-II | €127.54 | Amazon |
| LEAP digital chess clocks (several models, some with a byo-yomi preset) | US$19–37 · €43–50 | Amazon, eBay |
| Analogue "I-GO Count" clocks | US$29.95–37.22 | eBay, Walmart marketplace |
| Citizen The Meijin-sen DIT-50 (Japan) | ¥16,500–19,800 | Amazon.co.jp, Yahoo! Shopping |
| Seiko BZ361L (Japan) | ¥7,700–13,200 | Kiseido-style Go shops, the Shogi Association store |
Two things stand out. First, the price of a device that genuinely does byo-yomi starts around €30 and the Japanese club-standard machines cost several times that. Second, most of what a search for a "Go clock" returns is a chess clock — and a chess clock's delay or increment mode is not byo-yomi. See chess clock vs Go clock for why the two are not interchangeable.
Where the hardware genuinely wins
- Tournament use. Where an event's regulations specify a physical clock, that settles it — no app changes what the rules say. Ask the director before the round.
- The button. A big mechanical seesaw button under the heel of your hand gives a click you can feel. In a scramble, many players prefer that to glass.
- It only does this. No call interrupts it and no notification covers it — it is not competing with everything else a phone is doing.
- It survives the club. A device that lives in the club box gets dropped. Phones do not enjoy that.
Where a phone wins
- Cost. The phone is already bought.
- Reading the count out loud. Byoyomi Timer says the seconds aloud, the way a human timekeeper does, so you can keep your eyes on the board.
- Every system, not the ones that fit on a dial. Byo-yomi, Canadian overtime with a stone counter, Fischer bonus time, Ing and NHK-style reserves, sudden death, time per move — see all seven. Hardware presets are finite; a screen is not.
- Asymmetric clocks. Different main time, different periods, even a different system per player — for handicap and teaching games. Almost no device does this.
- Fixing mistakes mid-game. Adjusting time, periods and stones without restarting.
- It is with you. The club clock is at the club. The phone is on the train, in the café, at the kitchen table.
The other apps
For completeness, the timing apps that actually rank alongside this one: Byo-Yomi Timer (Windows), Go Timer and Go-clock (Android), Go Clock Pro (iOS), and the browser-based Baduk Clock. Several are free. Rather than rate them here, apply the test on choosing a Go clock app: set a ten-second period, move in five, and check that the period returns to a full ten seconds and the period count has not dropped. An app that fails it has a delay mode wearing byo-yomi's name — run it yourself rather than take anyone's word, including ours. You can run the same test in the browser on our free online Go clock, before installing anything.
So which one
If you direct tournaments, or your event requires a physical clock, buy the device — the DGT 1005 is the one sold for byo-yomi, and in Japan the Citizen and Seiko models are what the shops carry. If you play at home, in a café, at a club that does not mandate hardware, or you want the seconds read out loud and every time system available, the phone does more for nothing. Many players end up with both: the club owns the clocks, and the app comes along for everything else.
Turn your iPhone into a real Go clock
Byoyomi Timer plays every Go time system — byo-yomi, Canadian overtime, Fischer bonus time, Ing — and reads the seconds aloud like a human timekeeper.
Coming soon to the App Store