無料オンライン時間持続計算機

Enter start time before midnight (e.g. 22:30) and end time after midnight (e.g. 02:15 the next day). Check the "Spans midnight" toggle and the calculator adds 24 hours to the end time before computing the difference.

Add durations individually using the addition mode. For summing a list of time values (work log entries, workout segments), enter each duration sequentially — the running total updates after each addition.

Decimal hours express time as a decimal number: 1h 30m = 1.5 hours; 2h 45m = 2.75 hours. Decimal hours are used in time tracking, billing, and payroll systems where hours are multiplied by hourly rates.

Enter your clock-in time as start and clock-out as end. Subtract your lunch break separately if unpaid. The calculator shows total worked hours in both HH:MM and decimal format for payroll calculation.

Yes. Use the "Start + Duration = End" mode: enter your start time and how long something takes (e.g. 3h 20m) to find what time it will end.

Yes, the 時間持続計算機 on Allio Tools is completely free with no sign-up or registration required. It works directly in your browser.

2つの時刻間の持続時間を時間、分、秒で計算します。 No data is sent to a server — everything runs locally in your browser for maximum privacy and speed.

No installation needed. The 時間持続計算機 runs entirely in your web browser on any device — desktop, tablet, or mobile.

Completely safe. The 時間持続計算機 processes everything locally in your browser. No input data, results, or usage information is ever transmitted to or stored on any server.

After the page loads for the first time, the 時間持続計算機 works without an internet connection for all client-side processing. Tools that fetch live external data (such as DNS or network lookups) require an active connection.

Yes. The 時間持続計算機 uses your browser's built-in time zone data, which includes daylight saving time rules for all supported time zones, keeping results accurate year-round.

The 時間持続計算機 uses your browser's built-in Intl and Date APIs, which automatically account for daylight saving time transitions, leap years, and regional time zone rules. You do not need to make any manual adjustments for these calendar events.

Yes. The 時間持続計算機 is built with standard browser APIs and works on all modern browsers including Chrome, Firefox, Safari, and Edge — on both desktop and mobile. No plugins, extensions, or third-party software are required.

Select and copy the result text to paste into any document or app. For image tools, a Download button saves the file directly to your device. Your browser's built-in screenshot function also captures results quickly. No account or login is required.