Binary Clock
NewWatch the current time displayed as a live Binary-Coded Decimal (BCD) clock, with each digit of hours, minutes, and seconds shown as a column of binary dots.
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A binary clock represents each decimal digit of the current hour, minute, and second as Binary-Coded Decimal (BCD) — a column of dots (4 bits for ones digits, 2-3 bits for tens digits depending on their maximum possible value) read from bottom (value 1) to top, where a lit dot counts and an unlit dot doesn't. Add up the lit dots' values in each column to read the decimal digit. This is a fun visual way to practice reading binary numbers, purely computed and updated client-side every second.
Frequently Asked Questions
How do I read a binary clock?
Each decimal digit (of hours, minutes, and seconds) gets its own column of dots, read from bottom to top with values 1, 2, 4, 8 — add up the values of the lit (filled) dots in a column to get that digit, then read the digits left to right as usual.
What does "Binary-Coded Decimal" (BCD) mean here?
Rather than converting the entire time into one giant binary number, BCD encodes each decimal digit separately in binary — so "47" minutes becomes the digit "4" (0100) and the digit "7" (0111) shown as two separate dot columns, not one binary number for "47" as a whole.
Why do some columns have only 2 dots while others have 4?
The tens digit of hours, minutes, and seconds only ever needs to represent 0-5 (or 0-2 for the hour's tens digit), which fits in 2 binary bits, while the ones digit can go up to 9 and needs the full 4 bits — so each column only shows as many dots as that digit actually requires.
Does this clock use my computer's actual system time?
Yes — it reads your device's local system clock directly in the browser and updates every second; nothing is sent to a server, and no network connection is required after the page loads.
Can I switch between 12-hour and 24-hour format?
Yes — toggle the "24-hour format" checkbox to switch, and in 12-hour mode an AM/PM label appears next to the readable time underneath the dot grid.