A practical place to plan your night
Sleep Calculator is an independent English-language sleep calculator and bedtime planning website. It is free to use, requires no account, and performs calculations in your browser. Its purpose is to make the relationship between bedtime, time to fall asleep and waking easy to understand.
Sleep Calculator is not a healthcare provider, a sleep laboratory or a medical device. We do not claim medical review, clinical validation, professional accreditation or a research team. The calculator is a transparent scheduling tool.
How the calculation works
For a wake-up target, we subtract the chosen sleep duration and estimated time to fall asleep. For a bedtime input, we add latency and then duration. If the input already represents sleep onset, latency is not added again. Sleep now reads the device’s current instant when the calculation is submitted.
Duration mode offers adult planning targets from seven to nine hours. Cycle mode multiplies four, five or six cycles by an assumed 80–100-minute length, defaulting to 90 minutes. Cycles are estimates, not a prediction of REM, deep sleep or the best instant to wake.
Dates and time zones are part of each result. Calculations use elapsed time across daylight-saving changes. Nonexistent local times are rejected; repeated local times require an explicit earlier/later choice. This avoids silently moving the time you entered.
How information is sourced
Health-related explanations prioritize the CDC, NIH/NHLBI and AASM. Each educational page links to its sources. The age table consistently uses the CDC’s published age bands, and explains where another authority uses a different boundary.
The visible review date means the sources were checked for the page’s educational content. It does not mean that a clinician reviewed the site. We do not publish invented testimonials, ratings, traffic numbers or expert endorsements.
The content was prepared with AI assistance and checked against the cited sources. It remains general educational material. If you notice an error, our Contact page explains how to report it when the support channel is active.
A simple data boundary
The site has no account system, medical profile or database of sleep plans. Inputs stay in the current browser session. Copying or sharing is your choice, and the site stores only a theme preference in local storage. See the Privacy Policy for the full description of current behavior.
Sleep Planner for iPhone
Sleep Planner brings the calculator to iPhone and adds weekly plans, optional bedtime reminders and a manual sleep journal. The app stores those plans and entries on your device.