Methodology & Sources
Last reviewed:
This page documents how every TinyTools calculator produces its result: the formula, the assumptions, and — for overtime rules and tax figures — the specific statute or government publication the number comes from. If a figure here is out of date or wrong, please tell us.
How the calculators are built
- One shared, tested engine. All calculators call the same open TypeScript library, so a time card, the overtime calculator, and the paycheck calculator agree with each other. It is covered by an automated test suite (200+ cases) that runs on every change.
- Money is handled in whole cents. Amounts are stored and added as integer cents and only formatted to dollars for display, so repeated operations do not accumulate floating-point rounding error.
- Everything runs in your browser. No inputs are sent to a server. The tools keep working offline once the page has loaded.
- Unsupported cases are stated, not guessed. If you pick a state, country, or tax year the engine does not have validated data for, the tool says so and withholds no number rather than inventing one.
Hours, time cards, and decimal hours
Elapsed time is end − start, plus 24 hours when the end time is
at or before the start time (an overnight shift), minus any unpaid break.
Decimal hours are hours + minutes ÷ 60. Optional rounding
applies the increment you choose (for example nearest 6 minutes = nearest
tenth of an hour) to each day before totals are summed. These are standard
timekeeping conventions; the accuracy of the result depends entirely on the
times you enter.
Overtime rules
The overtime presets are calculation settings, not legal advice. Whether you are entitled to overtime, and at what rate, depends on your employee classification, your award or contract, and current law where you work. The engine applies the threshold and multiplier for the rule you select:
| Preset | Rule applied | Primary source |
|---|---|---|
| US — federal (FLSA) | 1.5× the regular rate after 40 hours in a workweek | US Department of Labor, Wage and Hour Division — Overtime Pay (Fair Labor Standards Act, 29 U.S.C. §207) |
| US — California | 1.5× after 8 hours in a day or 40 in a week; 2× after 12 hours in a day. The 7th-consecutive-day rule is not modelled. | California Department of Industrial Relations — Overtime (Labor Code §510) |
| Canada — Ontario | 1.5× after 44 hours in a work week | Ontario — Your guide to the Employment Standards Act: Overtime |
| United Kingdom | No statutory overtime rate — pay is whatever the contract states. The 48-hour limit is an average cap for health and safety, not an overtime trigger. | GOV.UK — Overtime: your rights, GOV.UK — Maximum weekly working hours |
| Australia | A common modern-award pattern (often a 38-hour week, then 1.5× and 2×). Your actual award may differ. | Fair Work Ombudsman — Overtime pay |
| Custom | Your own threshold (hours) and multiplier | — |
Pay and salary conversions
Conversions between hourly, weekly, biweekly, semi-monthly, monthly, and annual pay use the hours-per-week and weeks-per-year values shown on the page. The default full-time year is 40 hours × 52 weeks = 2,080 hours. "Real hourly rate" divides annual pay by the hours actually worked after subtracting paid time off. These are arithmetic conventions, not a legal standard.
US paycheck & take-home pay — tax year 2026
The paycheck and take-home calculators estimate payroll withholding for US tax year 2026. Withholding is a running prepayment of your tax; the amount you ultimately owe is settled on your annual return. Every figure below is the value built into the engine and the source it was taken from.
Federal income tax withholding
- Method: the Percentage Method for Automated Payroll Systems (Worksheet 1A), annual payroll period, for a 2020-or-later Form W-4. Pre-2020 W-4s with allowances are not modelled.
- 2026 standard-deduction amounts embedded in the schedules: $16,100 single, $24,150 head of household, $32,200 married filing jointly.
- Source: IRS Publication 15-T, Federal Income Tax Withholding Methods (for use in 2026).
Social Security and Medicare (FICA)
- Social Security: 6.2% of wages up to the 2026 wage base of $184,500.
- Medicare: 1.45% of all wages, plus an Additional Medicare Tax of 0.9% on wages over $200,000 in a year (employers withhold this regardless of filing status).
- Sources: Social Security Administration — Contribution and Benefit Base; IRS — Additional Medicare Tax (Internal Revenue Code §3101).
State income tax withholding
Supported states only. Local city and county income taxes (for example New York City, Yonkers, and the Philadelphia wage tax) are never included.
| State | Rule applied (2026) | Source |
|---|---|---|
| California | Method B exact-calculation, annual payroll period, with the low-income exemption, standard deduction, and exemption-allowance credit | California EDD — Rates & Withholding (DE 44, California Withholding Schedules for 2026) |
| New York | Method II exact-calculation, annual tax rate schedule and Table A deduction/exemption allowance | NYS Department of Taxation and Finance — Withholding tax forms (Publication NYS-50-T-NYS) |
| Illinois | Flat 4.95%, with the 2026 personal exemption allowance of $2,925 per allowance | Illinois Department of Revenue — Withholding (Booklet IL-700-T) |
| Pennsylvania | Flat 3.07%, no allowances or standard deduction | Pennsylvania Department of Revenue — Employer Withholding |
| AK, FL, NH, NV, SD, TN, TX, WA, WY | No state income tax on wage income — $0 state withholding | Respective state revenue departments |
| Any other US state | Not yet supported — the tool shows federal and FICA only and says the state figure is missing | — |
What the paycheck tools do not model
- The tax you ultimately owe — credits, other income, and itemised deductions reconciled on your return.
- Local city or county income taxes.
- State disability and unemployment contributions beyond noted cases.
- Wage garnishments and post-tax benefit elections.
- Year-to-date wage-base tracking across multiple employers.
- Canada, the United Kingdom, and Australia — not yet supported for tax.
How this is kept current
Tax figures are reviewed against the source publications when the relevant agency releases the next year's tables, and the "last reviewed" date at the top of this page is updated. The applicable tax year is shown on every paycheck result. TinyTools is independent and is not affiliated with the IRS, the SSA, any state revenue body, or any other government agency; for an authoritative figure, use your employer's payroll system or an official government calculator. See also the Disclaimer.