Adding many short tasks: why rounding each one can distort the total
Rounding errors accumulate when every small interval is rounded before addition. Sum the original seconds first, then convert the total.
Time conversion →Try twenty short tasks
Twenty tasks lasting forty-five seconds each take 900 seconds in total. That is fifteen minutes, or 0.25 hours. Rounding each task down to zero whole minutes would incorrectly produce zero minutes overall. Rounding each up to one minute would instead produce twenty minutes. Both errors arise before the final unit conversion even begins.
Keep the original precision until the end
Store individual durations in seconds, add them and then choose a display in minutes or hours. An average task time of forty-five seconds is 0.75 minutes, not 0.45 minutes. The average tool can summarize observations once all entries use the same unit. Retaining the original observations also makes it possible to recalculate if a reporting format changes.
Display rules are not billing rules
Showing two decimal places is a formatting decision; it does not establish a contract’s minimum billing interval or a payroll convention. If an agreement requires separate rounding of each billable event, apply and explain that rule independently. This site converts time quantities and does not decide which billing rule applies or whether it is appropriate. Keep mathematical totals distinguishable from totals produced by a separate administrative rule.
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