{"success":true,"version":"v1","request":{"tool":"get_calculator_schema","calculator_id":"sleep-cycles"},"result":{"entity_type":"calculator","id":"sleep-cycles","calculator_id":"sleep-cycles","canonical_url":"https://tttkmbb.com/everyday/sleep-cycles","name":"Sleep Cycle Calculator","title":"Sleep Cycle Calculator – Bedtimes or Wake-up Times Aligned to 90-Minute Cycles","category":"everyday","category_name":"Everyday Life","tool_name":"calculate_sleep_cycle_times","featured_mcp_tool":false,"description":"Suggests bedtimes for a given wake-up time, or wake-up times for a given bedtime, so that sleep ends at the boundary of a full sleep cycle (default 90 minutes) after a typical time to fall asleep (default 14 minutes).","use_when":"You want to pick a bedtime or alarm time that completes 3–6 whole sleep cycles instead of waking mid-cycle.","do_not_use_when":"You have a sleep disorder or shift-work schedule needing clinical advice; cycle length varies between people and through the night, so treat the times as approximations.","inputs":[{"name":"mode","label":"I know my…","type":"enum","required":true,"values":[{"value":"wake_up_at","label":"Wake-up time (suggest bedtimes)","aliases":["wake","wake_up","alarm"]},{"value":"go_to_bed_at","label":"Bedtime (suggest wake-up times)","aliases":["bed","bedtime","sleep"]}],"description":"Whether the given time is the wake-up time or the time you go to bed.","example":"wake_up_at"},{"name":"time","label":"Time","type":"string","required":true,"description":"The known wake-up time or bedtime, 24-hour HH:MM.","example":"06:30"},{"name":"fall_asleep_minutes","label":"Time to fall asleep","type":"integer","unit":"min","required":false,"default":14,"min":0,"max":120,"description":"Average sleep-onset latency; 10–20 minutes is typical for healthy adults.","example":14},{"name":"cycle_minutes","label":"Sleep cycle length","type":"integer","unit":"min","required":false,"default":90,"min":60,"max":120,"description":"Length of one sleep cycle; 90 minutes is the usual average (range about 70–120).","example":90}],"outputs":[{"name":"suggested_times","label":"Suggested times","type":"string_list","decimals":4,"description":"Bedtimes (for wake_up_at, earliest first: 6, 5, 4, 3 cycles) or wake-up times (for go_to_bed_at: 3, 4, 5, 6 cycles), HH:MM."},{"name":"sleep_cycles","label":"Cycles","type":"number_list","decimals":4,"description":"Number of full cycles for each suggested time, in the same order."},{"name":"sleep_hours","label":"Sleep","type":"number_list","unit":"h","decimals":2,"description":"Hours of actual sleep for each suggested time."},{"name":"schedule","label":"Schedule","type":"list","decimals":2,"description":"Objects with cycles, time and sleep_hours for each suggestion."}],"input_schema":{"type":"object","properties":{"mode":{"description":"Whether the given time is the wake-up time or the time you go to bed.","type":"string","enum":["wake_up_at","go_to_bed_at"],"examples":["wake_up_at"]},"time":{"description":"The known wake-up time or bedtime, 24-hour HH:MM.","type":"string","examples":["06:30"]},"fall_asleep_minutes":{"description":"Average sleep-onset latency; 10–20 minutes is typical for healthy adults. Unit: min.","type":"integer","minimum":0,"maximum":120,"default":14,"examples":[14],"x-unit":"min"},"cycle_minutes":{"description":"Length of one sleep cycle; 90 minutes is the usual average (range about 70–120). Unit: min.","type":"integer","minimum":60,"maximum":120,"default":90,"examples":[90],"x-unit":"min"}},"additionalProperties":false,"required":["mode","time"]},"output_schema":{"type":"object","properties":{"suggested_times":{"description":"Bedtimes (for wake_up_at, earliest first: 6, 5, 4, 3 cycles) or wake-up times (for go_to_bed_at: 3, 4, 5, 6 cycles), HH:MM.","type":"array","items":{"type":"string"}},"sleep_cycles":{"description":"Number of full cycles for each suggested time, in the same order.","type":"array","items":{"type":"number"}},"sleep_hours":{"description":"Hours of actual sleep for each suggested time. Unit: h.","type":"array","items":{"type":"number"},"x-unit":"h"},"schedule":{"description":"Objects with cycles, time and sleep_hours for each suggestion.","type":"array"}}},"formula":"wake_up_at: bedtime = time − fall_asleep_minutes − n × cycle_minutes; go_to_bed_at: wake time = time + fall_asleep_minutes + n × cycle_minutes; n = 3…6 (4.5–9 h of sleep at 90-minute cycles)","method":"A night's sleep consists of 4–6 cycles of roughly 90 minutes that progress through light, deep and REM sleep; waking at the end of a cycle tends to feel less groggy. Adults are advised to sleep 7–9 hours, i.e. 5–6 cycles.","sources":[{"name":"NIH NINDS – Brain Basics: Understanding Sleep","url":"https://www.ninds.nih.gov/health-information/public-education/brain-basics/brain-basics-understanding-sleep","type":"government","retrieved_at":"2026-09-23"},{"name":"Sleep cycle (Wikipedia)","url":"https://en.wikipedia.org/wiki/Sleep_cycle","type":"reference","retrieved_at":"2026-09-23"}],"freshness":{"type":"static","max_age_seconds":null,"note":"Deterministic formula with fixed constants; results never go stale. Inputs supplied by the caller determine the output."},"examples":[{"name":"Wake up at 06:30","inputs":{"mode":"wake_up_at","time":"06:30"},"expected":{"suggested_times":["21:16","22:46","00:16","01:46"],"sleep_cycles":[6,5,4,3],"sleep_hours":[9,7.5,6,4.5]},"url":"https://tttkmbb.com/api/v1/calculate/sleep-cycles?mode=wake_up_at&time=06%3A30"},{"name":"Go to bed at 23:00","inputs":{"mode":"go_to_bed_at","time":"23:00"},"expected":{"suggested_times":["03:44","05:14","06:44","08:14"],"sleep_cycles":[3,4,5,6],"sleep_hours":[4.5,6,7.5,9]},"url":"https://tttkmbb.com/api/v1/calculate/sleep-cycles?mode=go_to_bed_at&time=23%3A00"}],"faq":[{"q":"Which suggestion should I choose?","a":"Prefer 5 or 6 cycles (7.5–9 h); 3–4 cycles is a fallback for a short night, not a healthy routine."},{"q":"Are sleep cycles really 90 minutes?","a":"On average. Individual cycles range from about 70 to 120 minutes and lengthen through the night, so the suggested times are estimates to be fine-tuned by how you feel on waking."}],"tags":["sleep calculator","sleep cycles","when to go to bed","wake up time","bedtime calculator"],"related":[{"calculator_id":"time-duration","reason":"Hours between bedtime and wake-up time."}],"links":{"html":"https://tttkmbb.com/everyday/sleep-cycles","markdown":"https://tttkmbb.com/everyday/sleep-cycles.md","json":"https://tttkmbb.com/everyday/sleep-cycles.json","api":"https://tttkmbb.com/api/v1/calculate/sleep-cycles","schema":"https://tttkmbb.com/api/v1/calculators/sleep-cycles","openapi":"https://tttkmbb.com/openapi.json","mcp":"https://tttkmbb.com/mcp"},"version":"v1","updated_at":"2026-09-23"},"timestamp":"2026-09-23T23:29:08Z"}