Time & Date calculator
Work out what percentage one span of time is of another — like 40 minutes of an hour — or the percentage increase or decrease between an old and a new duration, such as a race, lap, or task getting faster or slower.
Free, no signup — not legal, payroll, or professional advice.
Pick a mode below: what percentage a part is of a whole, or the percentage change between an old and a new time. Mix seconds, minutes, hours, and days freely — the calculator converts everything for you.
Part is this % of whole
66.67%
Whole is this % of part
150%
Part, as a duration
40m 0s
Whole, as a duration
1h 0m 0s
40 minutes is 66.67% of 1 hours (2,400 of 3,600 seconds).
At a glance
Percentage of a total
Percentage = (Part ÷ Whole) × 100Both times are first converted to seconds, so minutes, hours, and days on either side never need to match.
Percentage change
Change = ((New − Old) ÷ Old) × 100Negative means the new time is shorter (faster); positive means it grew longer.
A quick reference for the question asked most often — what percentage of an hour a given number of minutes represents, using the same (Part ÷ Whole) × 100 formula above:
| Minutes | % of an hour |
|---|---|
| 5 min | 8.33% |
| 10 min | 16.67% |
| 15 min | 25% |
| 20 min | 33.33% |
| 25 min | 41.67% |
| 30 min | 50% |
| 35 min | 58.33% |
| 40 min | 66.67% |
| 45 min | 75% |
| 50 min | 83.33% |
| 55 min | 91.67% |
| 60 min | 100% |
Percentage of a Total answers "what share is this?" — Percentage Change answers "how much did this improve or worsen?" Enter the earlier (old) time and the later (new) time in that mode: a shorter new time gives a negative percentage (a decrease — faster, or a time saving), and a longer new time gives a positive percentage (an increase). The "new time as % of old" row shows the same comparison the other way round, which is often the more intuitive figure for a time-reduction or time-improvement question — a task now taking 80% of its old time is a 20% time saving.
The formula depends on how the cells are stored:
=B2/C2*100 gives the percentage directly.h:mm, like 0:40 for 40 minutes): Excel and Sheets store these internally as a fraction of a 24-hour day, so =B2/C2 already returns the correct ratio — format that result cell as Percentage rather than multiplying by 100 again, which would inflate the answer 100×.Percentage of a total. What percentage of 5 minutes is 30 seconds? Converted to a common unit, 5 minutes is 300 seconds, and 30 ÷ 300 × 100 = 10%.
Percentage change. A runner’s 5K time improves from 28 minutes to 25 minutes 12 seconds. In seconds, that is 1,680 down to 1,512 — a difference of −168 seconds, or −168 ÷ 1,680 × 100 = −10%: the new time is 10% faster, and equivalently, 90% of the old time.
It expresses one span of time as a percentage of another. Convert both times to the same unit (seconds is simplest), then divide the part by the whole and multiply by 100: Percentage = (Part ÷ Whole) × 100. This calculator does that conversion and division for you, for any mix of seconds, minutes, hours, or days.
Decide what the hours are a percentage of. To turn hours worked into a percentage of a standard workday, for example, divide the hours worked by the length of that workday and multiply by 100 — 6 worked hours out of an 8-hour day is (6 ÷ 8) × 100 = 75%. Enter both values in Percentage of a Total mode above to get the exact figure for your own numbers.
The same division, just in minutes: (minutes ÷ total minutes) × 100. The most common version is minutes as a percentage of an hour — see the quick-reference table below for every 5-minute mark from 5 to 60.
40 minutes is 66.67% of an hour (40 ÷ 60 × 100). Enter 40 minutes as the part and 1 hour as the whole above, or use the "40 min of 1 hour" preset, to see the full breakdown.
20 minutes is 33.33% of an hour (20 ÷ 60 × 100), or one third.
5 minutes is 8.33% of an hour (5 ÷ 60 × 100), or one twelfth.
Switch to Percentage Change mode, enter the old (before) time and the new (after) time, and it computes (New − Old) ÷ Old × 100. A negative result means the new time is shorter — faster, or a time saving; a positive result means it grew longer.
It can do the underlying arithmetic — divide the nights or days with one parent by the total nights or days in the period (e.g. 365) in Percentage of a Total mode to get a parenting-time percentage, which is how many custody schedules describe a split. It is not a legal or court-specific calculator, though: some jurisdictions and guidelines count time a particular way (overnights only, awake hours, school-year vs. summer). Confirm the required counting method with your court, guideline, or attorney before relying on the figure.
This tool only performs the percentage division itself, not a child-support formula — many guidelines use a parenting-time percentage as one input among several (income, number of children, add-on expenses) in a larger statutory calculation this calculator does not model. Use it to check the time-share percentage itself, then apply your jurisdiction's guideline or worksheet for the support amount.
Divide part-time hours by the standard full-time hours for the same period and multiply by 100 — 24 hours a week against a 40-hour full-time week is (24 ÷ 40) × 100 = 60%. Enter both in Percentage of a Total mode with the "hours" unit on each side.
Yes, in both modes. Use Percentage of a Total to see what share of a total race or run time a single lap or split took. Use Percentage Change to compare two times directly — a new time against a previous one, or a single time against an average time — to get the percentage improvement (faster) or regression (slower).
Yes — Percentage of a Total mode with the time listened or watched as the part and the total runtime as the whole gives the percentage progress, e.g. 1 hour 12 minutes into a 9-hour audiobook is about 13%.
See the "In Excel or Sheets" section below — the formula depends on whether your cells hold real time values or plain numbers, and getting that wrong is the most common source of a wrong answer.
"Time and a half" describes overtime pay at 1.5× (150%) the normal hourly rate — it is a pay multiplier, not a change in the length of time itself. To calculate overtime pay, multiply the hourly rate by 1.5 (and by the overtime hours worked); this calculator computes ratios between two durations, not wages, so it is not the right tool for that specific question.
No — this is a free web calculator, not a downloadable app. It works the same in any modern browser on desktop or mobile, with no installation or account required.
Educational use disclaimer
This calculator performs plain percentage arithmetic on the durations you enter. It is not legal, family-law, payroll, or professional advice — a parenting-time, custody, or child-support percentage used in a legal filing may need a specific counting method required by your court or guideline, and an overtime or "time and a half" pay calculation needs your actual hourly rate, not just a time percentage. For legal, payroll, or contractual figures, confirm the required method with the relevant document, guideline, or a qualified professional.
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