Time card calculator: hours worked, breaks and overtime

A time card converts clock time into money, and the conversion is where the errors live. A shift that runs 7:15 to 17:45 is not 10.30 hours, and 7 hours 45 minutes is not 7.45 hours. Payroll works in decimal hours, so every minute has to be divided by 60 before it can be multiplied by a rate.

This calculator takes a shift start, a shift end, an unpaid break in minutes, the number of days worked per week and an hourly rate. It returns paid hours a day, hours on site, hours a week, regular hours, overtime hours over 40, weekly gross pay, the overtime premium inside that pay, unpaid break time across the week, annualized gross over 52 weeks and total hours a year.

The sections below cover the decimal conversion, overnight shifts, which breaks are paid, how rounding practices work, and why the weekly total rather than the daily one determines federal overtime.

#The formula

Convert both clock times to decimal hours, take the span, subtract the unpaid break, then scale to a week and split the week at 40 hours.

Formula: decimal hour = HH + MM / 60. span = end - start, plus 24 if the result is negative. paid hours a day = span - break minutes / 60. weekly hours = paid hours a day x days worked. regular = min(weekly, 40) and overtime = max(weekly - 40, 0). weekly gross = regular x rate + overtime x rate x 1.5.

Symbols: HH and MM are the hour and minute on a 24-hour clock; rate is the base hourly rate before taxes and deductions; the 1.5 multiplier is the federal overtime rate under the Fair Labor Standards Act for non-exempt employees on hours over 40 in a workweek.

The overtime premium shown separately is overtime x rate x 0.5. That is the extra half that overtime adds on top of what those hours would have paid at the base rate, and it is the figure worth watching, because it is what a schedule change actually costs or saves.

#A worked example, done by hand

Worked example: a shift from 7:15 to 17:45, a 45-minute unpaid break, 5 days a week, at an assumed rate of $24.00 an hour.

1. Convert the times: 7:15 = 7 + 15/60 = 7.25 and 17:45 = 17 + 45/60 = 17.75.
2. Span on site: 17.75 - 7.25 = 10.50 hours.
3. Unpaid break: 45 / 60 = 0.75 hours. Paid hours a day: 10.50 - 0.75 = 9.75.
4. Weekly hours: 9.75 x 5 = 48.75.
5. Split at 40: regular 40.00, overtime 48.75 - 40 = 8.75 hours.
6. Pay: 40 x 24.00 = $960.00 regular, plus 8.75 x 36.00 = $315.00 overtime, for $1,275.00 gross a week.
7. The premium inside that: 8.75 x 12.00 = $105.00.
8. Unpaid break across the week: 45 x 5 / 60 = 3.75 hours. Annualized over 52 weeks: 1,275.00 x 52 = $66,300, on 48.75 x 52 = 2,535 hours.

Note that the 3.75 hours of break time are on site and unpaid. Compare 2,535 paid hours a year against 2,730 hours actually committed to the employer before travel.

#Minutes to decimal hours

This is the single most common arithmetic error on a manual time sheet. Minutes divided by 60, not minutes written after a decimal point.

So 7 hours 45 minutes is 7.75 hours. Entered as 7.45 it understates the shift by 0.30 hours, which at an assumed $24 an hour is $7.20 a day, or 7.20 x 5 x 52 = $1,872 over a year of five-day weeks. The error is small per instance and systematic, which is the worst combination.

Going the other way, multiply the fraction by 60: 0.6 hours is 36 minutes, not 60 minutes of anything.

#Overnight shifts

When the end time is earlier than the start time, the shift crossed midnight. Adding 24 before subtracting handles it: a shift from 21:45 to 06:15 gives 6.25 - 21.75 = -15.50, and -15.50 + 24 = 8.50 hours on site. With a 30-minute unpaid break that is 8.00 paid hours.

Two things the arithmetic does not decide for you. First, which workday the hours belong to: employers define a fixed 24-hour workday and a fixed seven-day workweek, and an overnight shift is usually attributed by the day it starts. Second, shift differentials -- extra pay for nights or weekends -- are a separate rate that this model does not carry.

The 24-hour adjustment also assumes no shift is longer than 24 hours. For a split shift, run each segment separately and add the paid hours.

#Paid and unpaid breaks

Under federal rules administered by the Department of Labor, short rest breaks -- commonly around 5 to 20 minutes -- are treated as compensable hours worked and are included in the weekly total for overtime purposes. Bona fide meal periods, typically 30 minutes or longer, during which the employee is completely relieved of duty, are not hours worked and are not paid.

The practical test is duty, not duration. A lunch period spent answering the phone or watching a register is not a bona fide meal period, and time spent that way is generally compensable. State law can be stricter than the federal floor, and some states require paid rest periods or meal breaks of a specified length.

Enter only genuinely unpaid time in the break field. Here is what a break costs across a week on the shift above, at an assumed $24 an hour:

Each 15 minutes of unpaid break removes 1.25 hours from the week and, because the week is already past 40 hours, $45.00 of overtime-rate pay. Below 40 hours the same 15 minutes would be worth $30.00.

#Rounding and the quarter-hour convention

Many timekeeping systems round punches to the nearest 5, 10 or 15 minutes, most commonly the quarter hour. The idea such systems are built around is neutrality: a rule that moves punches up about as often as it moves them down leaves the paid total close to where the raw punches would have put it, while a rule that leans one way does not. Whether any particular rounding practice is permitted in your case turns on federal and state rules and on the facts of the job, so take that question to the Department of Labor, whose wage and hour guidance is linked in the sources below, or to your state labor agency.

The familiar version is the seven-minute rule: within a 15-minute block, the first 7 minutes round down and minutes 8 through 14 round up.

Rounding that only ever goes one way is a different matter. A system that always rounds a start punch forward and an end punch backward, costing 6 minutes a day, removes 6/60 x 5 x 52 = 26 hours a year -- about $624 at an assumed $24 rate.

#Why the week drives overtime

Federal overtime is a weekly test. Hours over 40 in a fixed, recurring seven-day workweek are paid at not less than one and one half times the regular rate for non-exempt employees. There is no federal requirement to pay overtime for a long single day, so four 10-hour days produce no federal overtime at all, while five 9-hour days produce 5 hours of it.

Some states add a daily overtime rule -- typically over 8 hours in a day, sometimes with a double-time tier beyond a longer threshold -- and where both apply, the calculation that produces more pay governs. This model applies the federal weekly test only. The overtime pay calculator breaks the premium down further.

#Where each input comes from

Start and end times should come from actual punches or a supervisor-approved record, not from the scheduled shift, since the two diverge on exactly the days that matter.

The break field should reflect unpaid time only, taken from the employer's policy. Days per week is the count of days actually worked in the workweek, which is what drives the weekly total and therefore the overtime split.

The rate is the base hourly rate. Where an employee earns shift differentials, non- discretionary bonuses or piece rates, the federal overtime multiplier applies to a "regular rate" that includes those components, which is higher than the base rate entered here.

The answer is most sensitive to days worked, because that input alone can push the week across the 40-hour line where each extra hour is worth 1.5 times as much.

#How to read the result

Paid hours a day is what the employer owes for; hours on site is what the day costs you. The gap between them, multiplied out across the year, is the clearest argument for or against a long unpaid lunch.

Weekly gross is before tax. To see the take-home figure, run it through the take-home pay calculator, and to compare an hourly schedule against a salaried offer, use the hourly to salary calculator. The real hourly wage calculator adds commuting and job-related costs.

The annualized figure multiplies one representative week by 52 and is a projection, not a forecast. It assumes every week looks like this one.

#What this model leaves out

• Unpaid weeks. Annualizing by 52 assumes no unpaid leave, no seasonal shutdown and no gap between jobs. Paid time off is neutral here; unpaid time is not.
• The regular rate. Bonuses, shift differentials and commissions raise the rate used for overtime under federal rules. Only the base rate is used here.
• Taxes and deductions. Every figure is gross.
• Daily and seventh-day overtime. State rules that pay overtime on long days or on a seventh consecutive day are not applied.
• Exempt status. Overtime protections apply to non-exempt employees. Salaried exempt employees are not owed the premium.
• Travel, on-call and preparatory time. Some of this is compensable under federal rules; none of it is captured by two punch times.
• Calendar drift. 52 weeks is 364 days, so a year contains 52 weeks and one or two extra days.

This is general information about how the arithmetic works, not legal advice on a specific employment situation.

#Common mistakes

Writing minutes after a decimal point. 8 hours 30 minutes is 8.50, not 8.30. Check the conversion table above.

Subtracting the break twice. If a system already excludes an automatic lunch deduction from the punch record, entering it again removes the same time twice.

Testing overtime day by day. The federal test is the weekly total. A 12-hour day inside a 36-hour week generates no federal overtime.

Using the scheduled shift instead of the worked shift. Early starts and late finishes are exactly the hours in dispute.

Ignoring an asymmetric rounding rule. Neutral rounding is fine over time; rounding that always favors one side is not, and six minutes a day compounds to 26 hours a year.

Treating a working lunch as unpaid. A meal period is only unpaid when the employee is relieved of all duties. For counting the days themselves, the date difference calculator handles pay periods and weekday totals.