Hours Calculator

Time Arithmetic Without the Off-By-One Errors

The 24-hour trick and overnight shifts

Clock subtraction breaks the moment a shift crosses midnight — 22:00 to 6:00 naively yields negative hours. The fix is mechanical: when the end time is at or before the start, add 24 hours first. This calculator applies it automatically, using 24-hour input to remove the AM/PM ambiguity that causes most manual mistakes (a '7 to 3' shift is either 8 hours or 20 depending on which meridiem you meant).

Break rules are law, not preference

Whether that 30-minute deduction is legitimate depends on jurisdiction. Federal US law requires no breaks at all, but where breaks exist, sub-20-minute rest breaks must be paid, while 30+ minute meal breaks can be unpaid only if fully work-free — eating at your desk while answering the phone is legally payable time. States layer on mandates: California requires a 30-minute meal break before hour five, with an hour of premium pay owed for each missed one. Auto-deducted breaks you actually worked through are a leading wage-claim category.

Rounding: the quiet payroll variable

Employers may legally round punches to the nearest quarter-hour under federal rules, provided rounding is neutral — the '7-minute rule' (7:53–8:07 all become 8:00) must average out over time, not systematically favor the company. Chronic one-directional rounding (clock-ins rounded up, outs rounded down) is recoverable in wage claims. Keeping your own start/stop log for a couple of pay periods is the simplest audit there is.

Minutes to decimal: the payroll conversion table

Payroll systems compute in decimal hours, timesheets get written in minutes, and the translation between them is where paychecks leak. Pin this table to the breakroom wall — the middle column is the exact conversion, the right column is what standard quarter-hour rounding turns it into.

The single most expensive misconception on this page: writing 7 hours 45 minutes as "7.45." That entry shortchanges the worker 18 minutes (0.75 − 0.45 = 0.30 decimal hours × 60), and at $22/hour it's $6.60 per occurrence — a recurring donation to payroll for anyone who makes the mistake weekly. The digits after the colon and the digits after the decimal point are different number systems, and every timesheet form that fails to say which one it wants generates this error at scale.

Shift patterns and their arithmetic traps

Certain schedules break naive time math predictably. Overnight shifts are handled here automatically (end ≤ start adds 24 hours), but split shifts — common in restaurants and transit — need each segment computed separately and summed, since a 10 AM–2 PM plus 5 PM–10 PM day is 9 hours, not the 12 that first-to-last subtraction yields. On-call and sleep-time arrangements have their own federal rules: for shifts of 24+ hours, employers and employees can agree to exclude up to 8 hours of sleep time, but only if adequate facilities exist and the employee actually gets 5+ uninterrupted hours — interrupted sleep converts back to paid time. Daylight saving transitions create the year's two strangest paychecks: the November "fall back" overnight shift genuinely works an extra hour (payable, and potentially the hour that triggers overtime), while the March shift works one less. Payroll systems that log wall-clock punches without timezone awareness quietly miscount both nights.

What people get wrong

• Writing clock notation into decimal fields. 7:30 is 7.50 hours, 7:20 is 7.33. The colon-to-decimal confusion is the top self-inflicted timesheet error, and it always rounds against whoever writes it.
• Subtracting breaks that were worked through. An auto-deducted 30-minute lunch you spent covering the phone is compensable time under the FLSA — and auto-deduction cases are a staple of wage-claim settlements. Note actual break time taken, not scheduled.
• Trusting first-to-last punch on split days. Compute each segment. Some states (California notably) also owe split-shift premiums when segments spread across a long day at minimum-wage-adjacent pay.
• Assuming AM/PM from context. "Worked 7 to 3" is 8 hours or 20 depending on meridiem. The 24-hour inputs here exist precisely because context-guessing is how legendary payroll errors happen.

Freelancers: hours as inventory

For hourly-billing independents, this arithmetic is revenue accounting, and two disciplines separate profitable freelancers from busy ones. Track to the actual minute, bill to the agreed increment: contracts commonly specify 6-minute (0.1-hour, the legal-industry standard) or 15-minute increments, and the rounding direction belongs in the contract, not in each invoice's improvisation. And separate billable from worked hours honestly — industry surveys consistently find independents billing only 50–60% of hours worked once admin, marketing, and scoping absorb their share, which means a target income of $80K at a 55% billable ratio and 2,000 worked hours needs a rate near $73/hour, not the $40 that naive division suggests. The decimal-hours habit pays a second dividend here: time-tracking exports, invoicing tools, and spreadsheets all speak decimal, and a freelancer whose raw notes are already in 0.25 steps closes the books in minutes instead of translating a week of colon-notation scribbles. The same session log doubles as scope-creep evidence — the politest rate-renegotiation argument ever written is an accurate time report.

Reading your paystub against your own log

A personal shift log earns its keep at the paystub, and the audit takes five minutes per period. Reconcile three lines: total hours against your log's decimal sum, the overtime split against the per-workweek (not per-period) rule, and the rate applied to OT hours — which must be 1.5× the regular rate including nondiscretionary bonuses and differentials, a legally distinct number from 1.5× base that payroll systems occasionally miss. Discrepancies under a quarter hour are usually rounding doing its lawful, neutral thing; a pattern of round-downs across periods is the unlawful version and, documented across a few pay cycles, is exactly the evidence wage claims are built from. Federal statute of limitations runs two years (three for willful violations), so a shoebox of old logs has genuine monetary value.

Salaried readers: what your hours are worth anyway

Exempt employees don't punch clocks, but the hours-to-dollars division still matters — in reverse. A $75,000 salary at an honest 45-hour week is $32.05/hour; the same salary at the advertised 40 is $36.06, and knowing your real effective rate reframes everything from overtime-culture jobs to consulting side offers. The division also settles the classic exempt-versus-hourly job comparison: a $70K salaried role averaging 50 hours pays an effective $26.92, which a $30/hour position with actual overtime beats handily at the same schedule ($33.75 blended at 50 hours). Tracking a normal month of your own hours — this calculator, one line a day — is the cheapest career analysis available, and it occasionally surfaces the misclassification question worth asking: exemption requires a duties test, not just a salary, and salaried workers doing primarily non-exempt work have recovered years of back overtime.

Where the rules come from

The compensable-time framework is the Fair Labor Standards Act as interpreted in 29 CFR Part 785 — the sections covering meal periods (785.19: bona fide meal breaks must be duty-free), rest breaks (785.18: under 20 minutes is paid time), on-call and sleep time (785.20–23), and the rounding practice rule (785.48: rounding is lawful only when it averages out neutrally). The quarter-hour convention and the 7-minute breakpoint descend directly from that regulation. State layers vary meaningfully — California's daily overtime, meal-premium, and split-shift rules are the most protective — and the controlling document for any specific dispute is your state's wage order plus the federal floor, whichever is more generous to the worker.

Frequently asked questions

How do I convert minutes to decimal hours?

Divide by 60: 20 min = 0.33, 40 min = 0.67, 45 min = 0.75. The common error is writing 7:45 as 7.45 instead of 7.75 — a 30-minute underpayment every time it happens.

Does this handle shifts spanning midnight?

Yes — when the end time is at or before the start time, the calculator assumes the shift crossed midnight and adds 24 hours. A 22:00 start with a 6:00 end returns 8 hours.

Are lunch breaks always unpaid?

Only when they're bona fide meal periods — typically 30+ minutes, fully relieved of duty. Working lunches are compensable time under US federal law, and several states require meal-break premiums when breaks are missed or interrupted.

How do I add up multiple shifts in a week?

Convert each shift to decimal hours first, then sum the decimals — adding hours-and-minutes columns invites carrying errors. Five shifts of 7.50, 8.25, 7.75, 8.00, and 6.50 total 38.00 flat; the same addition done in h:mm notation is where 40-hour weeks mysteriously become 39:20.

Is travel time between job sites paid?

Travel between sites during the workday is compensable under the FLSA; the ordinary home-to-first-site commute isn't. The gray zones — mandatory shop stops before driving out, overnight travel for work — are governed by 29 CFR 785.33–41 and are worth reading if your week includes them, since they're frequently miscounted.