Time calculator — add or subtract durations
Blank fields count as zero · up to 10 rows
Time between two points
End earlier than start counts into the next day
Need dates, time zones, or a full breakdown? Time Duration Calculator
Clock time ± duration
e.g. 11:30 PM + 2h 45m = 2:15 AM next day
Expression
Tokens: 1d 2h 30m 45s or 1:30 literals, joined with + and −
RESULT
04:15:00
2h 30m + 1h 45m · the time calculator recalculates as you type
Add or subtract hours, minutes and seconds, find the elapsed time between two clock times, or shift a time across midnight. This free time calculator gives every answer as HH:MM:SS and decimal hours at once — ready to copy or share.
A shift from 21:45 to 06:15 — subtract the clock numbers and you get −15.5 h. Count through midnight and the true elapsed time is 8 h 30 m.
FIG. 2 — THE DECIMAL TRAP
Type 7:45 into a normal calculator and it reads 7.45. But 45 minutes fills three quarters of the hour — the decimal value is 7.75.
Payroll depends on that difference. Two-way conversion lives in the Time to Decimal Calculator.
FIG. 3 — CARRY AT SIXTY
50 m + 25 m = 75 m → 1 h 15 m
A time adder carries minutes into hours at sixty and hours into days at twenty-four — so 75 minutes can never be 0.75 of anything.
01
Stack up to ten rows of days, hours, minutes and seconds — the total carries at sixty as you type.
02
Flip any row to minus. If the answer goes negative you see the sign and the reason, never a silent zero.
03
Start and end times in AM/PM or 24-hour form; spans that cross midnight count into the next day.
04
Every result prints HH:MM:SS beside decimal hours, total minutes and total seconds.
05
Copy any single format, export the set as CSV, or share a link that restores the exact calculation.
06
Calculations run locally in your browser — nothing you type is uploaded anywhere.
2:30:00 + 1:45:00
= 9,000 s + 6,300 s
= 15,300 s → 4:15:00
A time calculator is a calculator built for base-60 quantities: it adds and subtracts durations, measures elapsed time between two points, and moves clock times forward or backward — jobs a decimal calculator gets wrong because an hour has sixty minutes, not a hundred.
Punch 2.30 + 1.45 into a desk calculator and you get 3.75 — but two and a half hours plus an hour and three quarters is 4 h 15 m. This site converts every entry to whole seconds, adds or subtracts them as integers, then rebuilds the clock form, so the sixty-carry can never be missed.
When an end time lands before its start, the span is counted into the next day and labeled so — an 11:00 PM to 6:00 AM shift is seven hours, not minus seventeen. And subtracting time past zero produces an honest negative duration, minus sign in every format, instead of a silently clamped result.
NIST's Times of Day FAQs calls 12 a.m. and 12 p.m. ambiguous, so the inputs also support 24-hour notation.
Decimal days and decimal hours are printed from the exact second count: 15,300 seconds is 4.25 hours because 15,300 ÷ 3,600 is exactly 4.25. Fixed precision, trailing zeros trimmed, and no rounding anywhere in the middle of a calculation.
Add up billable hours and minutes, then read the decimal form straight into an invoice.
Check a timesheet total by hand before it goes into the system — in, out, minus the break.
Time arithmetic homework, exam pacing, lab timing — with the working shown for every answer.
Overnight spans that cross midnight, counted the way the roster means them.
Cooking stages, workout splits, travel legs — everyday time addition without the mental carry.
STEP 01
Add or subtract time, elapsed time between two points, clock ± duration, or a typed expression.
STEP 02
Digits only, blank counts as zero, and overflow like 90 minutes normalizes on its own.
STEP 03
One calculation, four formats — clock, decimal hours, minutes, seconds — recalculated as you type.
STEP 04
Every format has its own copy button; the share link carries your inputs in the URL.
DURATION → SECONDS
t = 86,400·d + 3,600·h + 60·m + s
TIME BETWEEN
span = t₂ − t₁ + (t₂ < t₁ ? 86,400 : 0)
DECIMAL HOURS
H = t / 3,600 → 4 dp
CLOCK SHIFT
clock = ((t₀ + Δ) mod 86,400 + 86,400) mod 86,400
CARRY BACK
s → m at 60 → h at 60 → d at 24
Hours only, by design — rate and overtime math belongs on the Time Card Calculator.
23:30 + 2:00 = 25:30 raw
25:30 − 24:00 = 1:30 AM next day
The same integer-second engine converts payroll decimals on Time to Decimal and prices overtime on Time and a Half.
Type them as they are — 2 h 30 m plus 1 h 45 m. This time calculator converts everything to seconds internally, does integer arithmetic, and carries minutes at sixty on the way back out, so the answer is 4 h 15 m, never 3.75-something. Blank fields count as zero, and overflow values like 90 minutes normalize automatically.
One row per day in Add/Subtract mode: an 8:30 AM to 5:15 PM day minus a 45-minute break is 8 hours — five such rows total 40:00:00, shown beside 40.0 decimal hours for payroll. For clock-in/clock-out entry with break deduction and a printable weekly report, use the Time Card Calculator.
In Time Between mode an end time earlier than the start is treated as the next day and labeled that way. 11:00 PM to 1:30 AM is 2 h 30 m, not a negative number — the time calculator adds 24 hours once and tells you it did. Spans longer than one midnight need explicit dates, which the Time Duration Calculator handles.
Every result here already shows decimal hours next to the clock form: 7 h 45 m reads 7.75, because 45 minutes is 45/60 = 0.75 of an hour — not 0.45. For batch conversion in both directions, including decimal-to-clock, use the Time to Decimal Calculator.
Switch a row’s operator to minus. To take 45 minutes off 2 h 30 m, set the second row to − and type 45 minutes: the answer is 1 h 45 m. Subtract past zero and the result flips to an honest negative duration — minus sign in every format, with a note saying why.
Yes. Totals roll up into days — 30 h 90 m normalizes to 1 day, 07:30:00 — and the decimal, total-minutes and total-seconds formats keep counting past any day boundary.
Tokens like 1d, 2h, 30m, 45s, clock literals like 1:30, and the + and − operators. Consecutive tokens sum, so 1d 2h 30m + 45m - 20s evaluates to 1 day, 03:14:40. Anything the parser cannot read is highlighted in place as you type.
Yes — free, no sign-up, no install, no usage limits. Calculations run locally in your browser.
Exact to the second. All arithmetic happens on integer seconds; decimal forms are printed from that exact count to fixed precision and never rounded mid-calculation. The formulas and the full test suite are public on the methodology page.
Accuracy. Integer-second arithmetic, exact to the second. Formulas and test cases are public on the methodology page.
Privacy. Calculations run locally in your browser. See the privacy policy for what third-party scripts may process.
UPDATED 2026-08-01