{"$schema":"https://toolsly.tools/schemas/tool-manifest-v1.json","generated":"2026-05-20T20:47:38.358Z","discovery":{"catalog":"https://toolsly.tools/tools.json","llmsTxt":"https://toolsly.tools/llms.txt","sitemap":"https://toolsly.tools/sitemap.xml"},"relatedTools":[{"slug":"bmi-calculator","name":"BMI Calculator","url":"https://toolsly.tools/bmi-calculator"},{"slug":"percentage-calculator","name":"Percentage Calculator","url":"https://toolsly.tools/percentage-calculator"},{"slug":"age-calculator","name":"Age Calculator","url":"https://toolsly.tools/age-calculator"},{"slug":"date-difference","name":"Date Difference Calculator","url":"https://toolsly.tools/date-difference"},{"slug":"tip-calculator","name":"Tip Calculator","url":"https://toolsly.tools/tip-calculator"},{"slug":"timezone-converter","name":"Timezone Converter","url":"https://toolsly.tools/timezone-converter"},{"slug":"aspect-ratio-calculator","name":"Aspect Ratio Calculator","url":"https://toolsly.tools/aspect-ratio-calculator"},{"slug":"bytes-converter","name":"Bytes Converter","url":"https://toolsly.tools/bytes-converter"}],"kind":"utility","slug":"stopwatch","name":"Stopwatch (Duration Calculator)","description":"Format, add, or subtract durations like '1:23:45' or '1h 30m'. Heads up — this is a calculator, not a live stopwatch.","longDescription":"Drop in durations in any common format ('1:23:45', '90:00', '1h 30m', '2.5h', '90s') and format, add, or subtract them. Output is given in HH:MM:SS, total seconds, and a human-readable form like '1h 30m 45s'. Heads up: this is a calculator, not a real-time stopwatch — for an interactive timer you can start and stop, use your phone's clock app. This tool is for the 'how long total did I spend on X' or 'what's 1h 25m plus 47 minutes' kind of question. Runs entirely in your browser.","category":"calc","categoryName":"Calculators","keywords":["stopwatch","duration calculator","time duration add","time calculator","add hours and minutes","subtract time","time difference calculator","duration formatter","hms calculator","hours minutes seconds","elapsed time","time arithmetic","duration math","format duration"],"badge":"Calculator","url":"https://toolsly.tools/stopwatch","inputs":[{"type":"select","key":"mode","label":"Mode","defaultValue":"format","choices":[{"value":"format","label":"Format duration"},{"value":"add","label":"Add durations"},{"value":"sub","label":"Subtract durations"}]},{"type":"text","key":"a","label":"Duration A","defaultValue":"1:23:45","placeholder":"1:23:45 / 1h 23m 45s / 90s"},{"type":"text","key":"b","label":"Duration B","defaultValue":"45m","placeholder":"Only used for add / subtract","help":"Ignored in Format mode."}],"outputs":[{"key":"result","label":"Result (HH:MM:SS)"},{"key":"humanReadable","label":"Human-readable"},{"key":"totalSeconds","label":"Total seconds"},{"key":"totalMinutes","label":"Total minutes"},{"key":"totalHours","label":"Total hours"}],"invocation":{"webUi":"https://toolsly.tools/stopwatch","api":null,"notes":"Currently invoked via the web UI at `webUi`. Inputs are form fields; outputs are structured text values. A remote MCP/REST API is planned."}}