Enter durations in the correct format
Sum durations takes one entry per line. MM:SS represents minutes and seconds; HH:MM:SS represents hours, minutes and seconds. Thus 1:30 is one minute and thirty seconds, while 1:30:00 is one hour and thirty minutes. A duration describes an interval, not a clock time on a particular day.
Final minute and second fields must be between 00 and 59. The first field can exceed 59, and negative durations are not accepted. Up to ten thousand rows can be added. Inspect a short and a long entry before pasting a complete list to avoid silently interpreting hours as minutes.
Check the total and the scope of the sum
Adding 01:30 and 00:45 produces 0:02:15, or 135 seconds. The tool also displays entry count and decimal hours. One hour and thirty minutes is 1.5 hours rather than 1.30 hours: decimal values and colon-separated formats express quantities in different ways, so they should not be substituted without conversion.
Decide whether the sum includes breaks, waiting periods or only content. The tool cannot know that two entries overlap and will add both. Keep identifying labels outside the duration input when you need to trace the total. Copy or download output before editing the inputs that produced it so your saved record matches the original calculation.
Estimate transfers with bits and bytes
Transfer time divides size in bits by effective speed. MB and GB are decimal units, while MiB and GiB are binary. Mbps means megabits per second; MB/s means megabytes per second. One byte contains eight bits, making a mistaken unit selection a substantial change to the estimate.
For 100 MB at 100 Mbps and 100% efficiency, estimated time is eight seconds. At 50% efficiency, it is sixteen seconds. Efficiency reduces effective speed rather than measuring your connection. Latency, waiting, server variation and interruptions are not automatically included. Supply measured or documented values appropriate to your case instead of treating the general estimate as a live speed test.
Relate distance, duration and average speed
Average speed divides distance by the total duration you enter, including any stops covered by that duration. Ten kilometers in thirty minutes gives 20 km/h. This differs from a simple average of speeds recorded on segments with unequal durations, so define the scope of both distance and time before calculating.
Use hours for long durations; minutes range from 0 to 59 and seconds from 0 to less than 60. Verify whether distance is in kilometers, meters or miles. Unit conversion helps compare equivalent expressions of the same quantity. Keep the unit with every result and review plausibility, scope and rounding before reusing the number in another context.
Two durations and a transfer
Paste both rows into Sum durations and calculate. They represent one minute thirty seconds and forty-five seconds. Then try Transfer time with 100 MB, 100 Mbps and 100% efficiency.
01:30 00:45
The sum is 0:02:15, equivalent to 135 seconds. The transfer estimate is eight seconds; reducing efficiency to 50% gives sixteen seconds.
Do not replace Mbps with MB/s without accounting for their different meanings. For average speed, 10 km over 30 minutes gives 20 km/h. Retain units and which pauses the duration includes.