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Methodology

How we calculate

Every number on Leftover Planner comes from a published source and a formula you can check. This page explains both, in plain language.

Figures for tax year 2026. Last reviewed: October 2026

On this page: Money planner · Paycheck calculator · Tax refund estimator · Benefits checker · Borrowing costs · How we test · All sources

Money planner

  • Monthly amounts. Pay and bills on other schedules are converted with 52 weeks and 12 months a year. Weekly pay × 52 ÷ 12, every two weeks × 26 ÷ 12, and so on.
  • Leftover = monthly take-home pay − needs − wants − minimum debt payments.
  • The order your leftover goes in: a $1,000 starter emergency fund, then your full 401(k) match if you have one, then extra payments on debts at 8% interest or more, then a full emergency fund of 3 or 6 months of needs plus minimum payments, then your savings goal, then optional extra on lower-interest debt, then investing.
  • Interest is charged each month as APR ÷ 12 on the balance. Lenders that charge daily interest can differ by a few dollars.
  • Avalanche sends extra money to the highest interest rate first. Snowball sends it to the smallest balance first. When a debt is paid off, its minimum rolls into the next one.
  • Interest saved compares your plan with paying only the minimums, month by month, for up to 40 years.
  • Investment growth uses the yearly rate you choose (7% by default), compounded monthly. 7% is roughly the long-run average of broad U.S. stock funds after inflation, so results are in today's dollars. Real returns vary a lot from year to year.
  • Paycheck calendar lists your next paydays from your schedule and assigns each bill to the last paycheck before its due date.

Paycheck calculator

  • Federal income tax follows the IRS percentage method for automated payroll in Publication 15-T (2026), Worksheet 1A, using your W-4 answers: filing status, the Step 2 box, $2,200 per child and $500 per other dependent in Step 3, and Steps 4(a) to 4(c).
  • Social Security is 6.2% of wages up to $184,500. Medicare is 1.45%, plus 0.9% on wages over $200,000. Pre-tax health insurance and HSA contributions are excluded; traditional 401(k) contributions are not.
  • No tax on tips and overtime. If you choose to claim them on your W-4, up to $25,000 of tips and up to $12,500 ($25,000 married filing jointly) of the overtime premium are subtracted, phasing out above $150,000 ($300,000 jointly).
  • State income tax uses each state's 2026 brackets, standard deduction, exemptions and credits from the Tax Foundation's 2026 table, with special rules for states like Alabama, Ohio, Utah, Wisconsin and Connecticut. Each state's treatment of pre-tax benefits is followed, such as Pennsylvania taxing 401(k) contributions.
  • State payroll deductions include disability and paid leave programs (for example California SDI 1.3%, New York Paid Family Leave 0.432%, Washington Paid Leave and WA Cares) at their 2026 rates and wage caps.
  • Local taxes use the rate you enter. New York City tax uses the city's 2026 brackets.
  • Limits. Bonuses and other supplemental pay, some state withholding tables that differ from the yearly tax, and benefits like union dues aren't included. Results usually land within a few dollars of a real pay stub.

Tax refund estimator

  • Taxable income = income − 2026 standard deduction ($16,100 single, $32,200 married filing jointly, $24,150 head of household, plus extra for age 65+) − the new deductions for tips, overtime, seniors ($6,000 each) and car loan interest (up to $10,000), with their income phase-outs. Tax uses the 2026 federal brackets.
  • Credits: the Saver's Credit (50%, 20% or 10% of up to $2,000 in retirement savings per person), the $500 credit for other dependents, the Child Tax Credit of $2,200 per child with up to $1,700 refundable (15% of earnings above $2,500), and the Earned Income Tax Credit using the 2026 IRS table.
  • Refund = tax withheld + refundable credits − tax after credits. State taxes and many less common situations aren't included.

Benefits checker

  • Income limits are based on the 2026 HHS poverty guidelines ($15,960 for one person plus $5,680 for each additional person, higher in Alaska and Hawaii).
  • SNAP uses USDA's limits for October 2026 to September 2027, each state's gross income limit, and the federal net income test with the 20% earnings deduction, standard deduction and capped shelter deduction.
  • Medicaid and CHIP use each state's expansion status and children's limits from KFF. Marketplace help uses 100% to 400% of the poverty guideline. Other programs (WIC, school meals, Lifeline, LIHEAP, child care) use their federal rules.
  • It can only say “you may qualify.” Only the agency that runs a program can decide, and states have extra rules about assets, immigration status, age and more.

Borrowing costs

Each option's cost is calculated in dollars for the amount and time you choose, using typical prices you can change: payday loans at $15 per $100 every two weeks (CFPB), title loans at 25% a month, $35 overdraft fees, a 22.36% credit card APR (Federal Reserve average), cash advances at 29.99% plus a 5% fee, credit union payday alternative loans at 28% plus a $20 fee, and personal loans at 25% plus a 5% fee. APRs include fees.

How we test

Before any update goes live, the calculators are checked against examples worked by hand from the IRS and state formulas, every state is run at several incomes and filing statuses to catch errors, and every page and link on the site is tested in English and Spanish, on desktop and phone, in light and dark mode.

All sources

Each tool also lists the specific sources it uses at the bottom of its page.

Leftover Planner is an independent educational website. It is not affiliated with or endorsed by the IRS, USDA, HHS, the CFPB or any other government agency, and its results are estimates, not financial, tax or legal advice. Spot something wrong? Email hello@leftoverplanner.com.