Work hours overlap percentage calculator

You send six numbers—offset, start, and end for team A and the same three for team B—and the solver maps both windows onto a twenty-four-hour UTC circle, intersects them, and returns overlap minutes, overlap hours, the share of each team's day that is live-shared, and a headline overlap_percent equal to one hundred times the intersection over the shorter working day.

How two working days become an overlap percentage

Both days last eight hours, so the shorter day is eight hours and overlap_percent is one hundred times three over eight, or thirty-seven point five percent. The same identity is written on every successful response: utc equals local minus offset, modulo twenty-four hours; overlap is the intersection of the two UTC intervals on a circular day; overlap_percent equals one hundred times overlap_minutes divided by the minimum of team_a_minutes and team_b_minutes. Per-team fields overlap_percent_a and overlap_percent_b use each team's own duration as the denominator so a four-hour desk that sits entirely inside an eight-hour desk reports one hundred percent for the short team and fifty percent for the long team, while the headline figure stays one hundred percent because every minute of the shorter day is concurrent.

Input contract, response fields, and validation rules

Hours may be fractional. POST a JSON object with six required finite numbers. offset_a and offset_b are fixed UTC offsets in hours, each inside minus fourteen through plus fourteen inclusive; aliases include utc_a, team_a_offset, a_offset and the matching B names. start_a, end_a, start_b, and end_b are local clock hours from zero through twenty-four inclusive; aliases include team_a_start, a_start, team_a_end, a_end and the matching B names. When end_a is earlier than start_a the A window wraps midnight; the same rule applies to B. On success the body echoes the six rounded inputs and offset labels such as UTC−5, reports team_a_hours, team_b_hours, team_a_minutes, and team_b_minutes, publishes each window in UTC as team_a_utc_start, team_a_utc_end, team_b_utc_start, and team_b_utc_end with team_a_wraps and team_b_wraps booleans, and gives overlap_minutes, overlap_hours, overlap_percent, overlap_percent_a, overlap_percent_b, overlap_windows as an array of UTC start and end clocks, same_window when the two UTC intervals are identical, a one-line message, and the formula string. Example: offset_a minus five, start_a nine, end_a seventeen, offset_b zero, start_b nine, end_b seventeen yields three overlap hours, thirty-seven point five percent, and a single UTC window from 14:00 to 17:00. Failed validation—missing fields, non-finite values, an offset whose absolute value exceeds fourteen, a start or end outside zero to twenty-four, or a zero-length day—returns invalid_input naming the field and is never billed. Successful calls cost the published $0.002 base price with unit item.

Where a work-hours overlap percentage earns its keep

People operations teams use a work hours overlap percentage calculator when they write core-collaboration hours for a company split across two hubs: if New York and London share only three of eight hours, a policy that demands four live hours is not feasible without stretching one side. Invalid offsets and zero-length days do not consume balance. Keep offsets as the UTC± numbers already printed on tickets and server configs; this tool does not resolve IANA names such as America/New_York and does not apply daylight-saving transitions. If a region changes offset in March, send the winter number or the summer number you actually mean. Staffing models convert overlap_hours into concurrent seat counts so a follow-the-sun support roster does not pretend that a Tokyo morning and a California morning are the same shift. Sales and customer-success orgs schedule recurring calls in the intersection published as overlap_windows rather than guessing from a world clock. Contracting language that promises a minimum shared day can pin overlap_percent in a test instead of a screenshot. Pair examples when teaching: identical offsets and hours return one hundred percent and same_window true; New York versus London at nine to five returns thirty-seven point five percent; Tokyo nine to eighteen versus San Francisco nine to eighteen returns a short wrap-aware slice; an offset of fifteen demonstrates the hard invalid_input path. Pin overlap_percent and overlap_minutes in tests and you get reproducible concurrency math for handbooks, SEO landings, and edge workers without standing up a timezone database of your own.