Alarm Time Calculator

Work out alarm time instantly with clear inputs, formula shown and shareable results.

About Alarm Time Calculator

Set the alarm for the time you must leave minus getting-ready time minus however long you actually spend snoozing. Being honest about the snooze habit is the point: nine minutes times three is nearly half an hour of fragmented, low-quality sleep.

Formula

Alarm time

alarm = leave time - preparation time - (snoozes x snooze interval)

Worked example

With the default values below, Alarm Time Calculator returns Set the alarm for (24h clock) of 7.20. Change any input above and every figure here is recalculated in your browser.

Inputs used

Time you must leave (24h): 8.25 h
Getting ready time: 45 min
Snoozes you will use: 2 snoozes
Snooze interval: 9 min

Results

Set the alarm for (24h clock): 7.20 h
Time you will actually get up (24h): 7.50 h
Time lost to snoozing: 18 min
Total time before leaving: 63 min

Step by step

1Values used
2Alarm time
3Set the alarm for (24h clock)= 7.20 h
4Time you will actually get up (24h)= 7.50 h
5Time lost to snoozing= 18 min
6Total time before leaving= 63 min

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why is the snooze interval nine minutes?

A quirk of mechanical clock gearing that became a convention, and digital clocks kept it for familiarity.

Is snoozing harmful?

It fragments the last sleep cycle and can worsen grogginess. Setting the alarm for the real getting-up time gives better quality sleep in the same window.