One time calculator instead of three
Most sites split this into separate tools: one page to add durations, another for the gap between two clock times, a third to convert hours to decimals. They're the same arithmetic — seconds in, seconds out — so this calculator does all three in tabs, and every answer is shown simultaneously as days-hours-minutes-seconds, hh:mm:ss, total minutes and decimal hours.
Add / subtract stacks any number of duration rows, each with its own +/− switch: film edit timings, workout splits, audiobook chapters, cooking stages. 1 h 45 m + 2 h 30 m = 4 h 15 m — and if one row is a pause you want removed, flip it to minus instead of re-typing everything.
Time between is the timesheet workhorse: enter a start and end clock time, and an unpaid break to deduct. 9:00 to 17:30 minus a 30-minute lunch is exactly 8.00 decimal hours — the number payroll actually multiplies by your rate. It also handles overnight shifts automatically: if the end time is earlier than the start, it assumes you crossed midnight (22:00 → 6:00 = 8 hours) and says so, instead of returning a negative.
The decimal-hours trap catches nearly everyone once: 7 hours 30 minutes is 7.5 hours, not 7.3, because minutes are sixtieths, not hundredths. Billing 7:45 as "7.45 hours" short-changes you 18 minutes every shift. The converter tab and the reference table above make the translation instant in both directions.
Everything runs in your browser — nothing you enter is sent anywhere — and the CSV button exports your rows and totals for a timesheet or invoice.