Sleep Calculator

All tools

Find the best times to fall asleep or wake up based on 90-minute sleep cycles, so you wake between cycles feeling refreshed rather than groggy.

min
– –
Based on 90-minute sleep cycles. 5 to 6 cycles (about 7.5 to 9 hours) suit most adults; waking between cycles helps you feel rested.
Related Tools
Date Difference Calculator

Calculate the time between two dates in years, months, days, weeks and hours, or add and subtract durations — with optional business days. Free, in your browser.
Age Calculator

Find your exact age in years, months and days from a date of birth, plus total months, weeks, days and hours and a countdown to your next birthday.
Date Add & Subtract Calculator

Add or subtract years, months, weeks and days from any date to find the resulting date, its weekday, ISO format and how many days it is from today.
Business Days Calculator

Count the working days between two dates, or add a number of business days to a start date, automatically skipping weekends.
Time Duration Calculator

Calculate the duration between a start and end time in hours and minutes, with totals in minutes, seconds and decimal hours, including overnight spans.
Online Timer

A simple, full-screen countdown timer with quick presets, a custom duration and an alarm when time is up. Free and runs in your browser.

Add this free tool to your own website — copy and paste the code below.