Why is the top still fairly full at the halfway mark?

Because the glass is drawn so that the amount of sand keeps time, not the height. The top bulb is widest at the top, so the first part of the time takes the wide upper layers and the level falls slowly, then it drops quickly near the neck. Halfway through, the level stands at about seven tenths of the bulb and each bulb holds exactly half the sand, which is how a cone-shaped glass behaves.

Can it be a 1, 3 or 5 minute sand timer?

Any length. The One countdown buttons set 1 to 60 minutes in one press, and an activity's minutes box takes a fraction of a minute, such as 0.5 for thirty seconds, up to 24 hours. The glass always runs from full to empty over the length you set.

Does it make a sound when the sand runs out?

Only if you ask. It opens silent, and At zero offers a soft chime or a bell. A browser plays nothing until you have pressed something on the page, and the line under the buttons says when it is still waiting for that press.

Does opening this page change my main classroom timer?

No. This page opens on the sand glass and the main classroom timer opens on digits, and the display you pick is not remembered on either. The list of activities is shared: a plan you build here is the one the main page shows next time in this browser, and the Start over button at the top of the page forgets it.

Classroom Sand Timer

The timer below opens as a sand timer, the kind sometimes called an egg timer: an hourglass whose top bulb empties into the bottom as the activity runs, with the time left in digits beneath it. Unlike a glass on the desk it runs for whatever length you set, a 1, 3 or 5 minute turn or a 45 minute task, and it never needs turning over. Press a length from 1 to 60 minutes for a single glass, or name several activities and the glass fills again for each one. Display switches to plain digits or to a disc at any time, and Full screen makes the glass big enough for the whole room.

Warm up · 1 of 4

05:00

4 activities, 26:00 in all

Silent at zero: the screen changes, nothing sounds

Now: Warm up
Whole plan: 26:00
At zero
Display

Ready. Press Start and the first activity begins; the countdown is read from your device clock.

One countdown

Activity 1
Minutes
ready
Activity 2
Minutes
waiting
Activity 3
Minutes
waiting
Activity 4
Minutes
waiting

Keys, when you are not typing in a box: Space starts and pauses, N moves to the next activity, R starts the plan again, F fills the screen. An activity that ends while the tab is away hands the next one the exact moment it finished, so several can go by and the timer still lands on the right one. It stays quiet about the ones it missed rather than playing a chime for each.

Reads the clock rather than counting ticks. The countdown is read from your device clock rather than counted, so a tab left in the background is still correct when you come back. It cannot make a browser play a sound before you have pressed something, and it says when it is waiting for that.

Common questions

Why is the top still fairly full at the halfway mark?: Because the glass is drawn so that the amount of sand keeps time, not the height. The top bulb is widest at the top, so the first part of the time takes the wide upper layers and the level falls slowly, then it drops quickly near the neck. Halfway through, the level stands at about seven tenths of the bulb and each bulb holds exactly half the sand, which is how a cone-shaped glass behaves.
Can it be a 1, 3 or 5 minute sand timer?: Any length. The One countdown buttons set 1 to 60 minutes in one press, and an activity's minutes box takes a fraction of a minute, such as 0.5 for thirty seconds, up to 24 hours. The glass always runs from full to empty over the length you set.
Does it make a sound when the sand runs out?: Only if you ask. It opens silent, and At zero offers a soft chime or a bell. A browser plays nothing until you have pressed something on the page, and the line under the buttons says when it is still waiting for that press.
Does opening this page change my main classroom timer?: No. This page opens on the sand glass and the main classroom timer opens on digits, and the display you pick is not remembered on either. The list of activities is shared: a plan you build here is the one the main page shows next time in this browser, and the Start over button at the top of the page forgets it.

The countdown is read from your device clock rather than counted, so a tab left in the background is still correct when you come back. It cannot make a browser play a sound before you have pressed something, and it says when it is waiting for that.