Overtime Calculator

An overtime calculator converts a work schedule into regular hours, overtime hours, premium pay, time off in lieu, gross pay and an estimated net amount. The tool helps when shifts cross midnight, employers use tiered overtime rates, night or weekend premiums apply, or the employee earns a monthly or annual salary rather than a stated hourly rate.

The calculator is a planning and checking tool. It does not decide whether overtime is legally payable. Entitlement can depend on the employment contract, collective agreement, worker status, sector, averaging period and the rules that apply in the country. Always compare the result with the payslip and the current official guidance.

What the overtime calculator can estimate

• base hourly rate from hourly, monthly or annual pay;
• worked hours after unpaid breaks;
• daily and weekly overtime without double-counting the same hour;
• first-tier and second-tier overtime rates;
• night, weekend and public-holiday premiums;
• paid overtime, time off in lieu or a split arrangement;
• shift bonuses;
• gross pay, estimated deductions and estimated net pay;
• monthly and annual projections;
• a shift-by-shift CSV record.

Step 1: calculate worked hours

For each shift, the basic formula is:

Worked hours = shift end − shift start − unpaid break.

If a shift starts at 22:00 and ends at 06:00, the end time belongs to the following day. The calculator therefore treats the shift as eight hours before breaks rather than a negative duration.

Enter a break only when the employer does not pay for it and the employee can stop working. The applicable rules may count a working lunch or any break during which the employee must continue working as working time.

Step 2: convert salary to an hourly rate

For an hourly worker, the calculator uses the entered rate directly. For a salaried worker, the calculator estimates:

Hourly rate from annual salary = annual salary ÷ contract hours per week ÷ paid weeks per year.

Hourly rate from monthly salary = monthly salary × 12 ÷ contract hours per week ÷ paid weeks per year.

This conversion may differ from payroll where the employer uses a fixed divisor, excludes certain allowances or calculates overtime from basic salary only. Use the rate defined by the contract or payslip whenever it is available.

Step 3: daily and weekly overtime

The calculator first identifies hours above the daily threshold. It then applies the weekly threshold only to the remaining regular-hour candidates. This sequence prevents the calculator from classifying one hour twice.

For example, assume a daily threshold of eight hours and a weekly threshold of 40 hours. A schedule of 8, 8, 8, 8 and 10 hours contains two daily overtime hours. The other 40 hours remain regular, so the final result is 40 regular hours and two overtime hours.

If there is no daily overtime rule, enter zero. The calculator will then classify overtime only from the weekly threshold.

Step 4: first and second overtime tiers

Some arrangements pay one multiplier for the first block of overtime and a higher multiplier after a threshold:

Tier 1 pay = tier 1 hours × hourly rate × tier 1 multiplier.

Tier 2 pay = tier 2 hours × hourly rate × tier 2 multiplier.

The second-tier threshold can reset each calendar week, continue across the entered pay period or use a monthly accumulation. The monthly mode also accepts overtime already worked earlier in the month.

Overtime multiplier and overtime premium

A multiplier of 1.5 means the employee receives the base rate plus an additional 50%. It is important not to add the base rate twice.

Total overtime rate = base rate × multiplier.

Overtime premium only = base rate × (multiplier − 1).

The calculator displays overtime pay separately from shift premiums so you can compare the result with a payslip.

Night, weekend and public-holiday premiums

Enter the number of night hours within each shift. Choose the weekend or public-holiday rate through the day-type field. The calculator supports two methods.

With additive stacking, the calculator adds every applicable premium. With highest-premium treatment, the calculator applies only the highest applicable premium to the relevant hours. Neither method is universally correct; the contract or collective agreement decides how premiums interact.

Paid overtime and time off in lieu

The employer may pay all overtime, convert it to time off in lieu, or split the compensation. The calculator uses:

TOIL hours = overtime hours × unpaid fraction × time-off multiplier.

If an agreement converts four overtime hours to leave at 1.5, the employee receives six hours of time off. Under a 50/50 arrangement, the employer pays half of the overtime compensation and converts the other half to time off.

Night or holiday premiums for regular hours remain separate from the treatment of overtime. Whether a specific premium is payable during TOIL arrangements depends on the governing agreement.

Gross pay and estimated deductions

The calculator totals regular pay, paid overtime, shift premiums and bonuses:

Gross pay = regular pay + paid overtime compensation + bonuses.

The calculator estimates deductions with editable flat percentages:

Deduction estimate = gross pay × tax rate + gross pay × social rate + fixed deduction.

Net estimate = gross pay − estimated deductions.

This is not a payroll-tax calculation. Real deductions can use tax bands, allowances, thresholds, pension rules, benefits, student loans and year-to-date adjustments.

Monthly and annual projections

The calculator measures the date range covered by the entered shifts and projects the same pattern over an average month or year. The calculator multiplies a one-week pattern by approximately 4.345 for a monthly estimate and by 52 for an annual estimate.

Projection does not guarantee future income. Public holidays, leave, seasonal demand, rotating rosters and overtime limits can change the actual result.

Overtime in the United Kingdom

In the UK, overtime usually means time worked beyond the normal hours fixed by the employment contract. GOV.UK states that employers do not generally have to pay a special overtime rate, although average pay for all hours worked must not fall below the National Minimum Wage. The contract normally explains the rate and calculation method.

Most workers must not work more than an average of 48 hours a week, normally averaged over 17 weeks, unless an adult worker signs a voluntary written opt-out or an exception applies. Paid overtime and unpaid overtime requested by the employer can count as working time.

Because UK law does not provide one universal overtime multiplier, the UK regional preset uses neutral multipliers. Enter the contractual rate, such as time-and-a-half, double time or ordinary rate.

What counts as working time

Working-time and pay rules do not always classify time in the same way. GOV.UK includes job-related training, working lunches, certain business travel, requested overtime and on-call time at the workplace in working time. The rules normally exclude ordinary commuting and genuine rest breaks.

If the employee has more than one job, combined working hours can be relevant to the average weekly limit. Because the calculator only analyses the shifts you enter, add all relevant work when you need a combined view.

Keeping reliable records

Record the date, start, end, break, day type, night hours and reason for overtime. Keep rota changes, clocking data, emails approving extra work and payslips. A CSV export creates a useful personal record but does not replace the employer’s official time system.

Common calculation mistakes

• subtracting a paid break as if it were unpaid;
• counting a shift across midnight as a negative duration;
• classifying the same hour as both daily and weekly overtime twice;
• using 50% as a multiplier of 0.5 instead of a total multiplier of 1.5;
• adding premiums when the agreement applies only the highest one;
• using gross deduction percentages as a precise tax calculation;
• projecting one unusually busy week across a whole year;
• assuming a regional preset creates a legal entitlement.

How to verify an overtime result

Compare the entered schedule with the clocking record, then check the base hourly divisor, overtime trigger, tier reset period, premium interaction and treatment of breaks. Recalculate one shift manually.

For a dispute, compare the result with the employment contract and payslip. In the UK, Acas can provide guidance on working hours and pay. For high-stakes questions, ask an employment adviser or payroll specialist to check the result.

Frequently asked questions

Official sources

• UK government guide: Overtime — your rights
• Working-hours guidance: Maximum weekly working hours
• Official calculation guide: Average working hours
• The Working Time Regulations 1998, regulation 4
• HSE: Rest breaks and daily rest

Information and links reviewed: 20 June 2026.