Methodology and data status

Every calculator on this site is a pure function of its inputs and a data file that names the document each figure was read from. This page states the rules in plain steps, lists what each tool leaves out, and shows the verification status of every data file.

Data status

"Verified" means two independent reads of the primary documents produced the same figures and a third pass tried to break the mechanics with the agency's own examples; "draft" means one read so far. The federal file was verified in an earlier project that shares this calculation engine. Verification method and dated notes for each file are shown below its rules.

Social Security claiming and break-even

Calculator: Social Security break-even calculator

The calculator applies the SSA's month-by-month reduction and delayed-retirement-credit rules to the visitor's birth date and primary insurance amount, then sums the benefits of two claiming ages month by month to find the break-even age.

1. The SSA birth month: someone born on the 1st is treated as born the previous month, and on January 1 as born the previous year.
2. Full retirement age by year of birth: to 1937: 65; to 1938: 65 and 2 months; to 1939: 65 and 4 months; to 1940: 65 and 6 months; to 1941: 65 and 8 months; to 1942: 65 and 10 months; to 1954: 66; to 1955: 66 and 2 months; to 1956: 66 and 4 months; to 1957: 66 and 6 months; to 1958: 66 and 8 months; to 1959: 66 and 10 months; 1960 and later: 67.
3. Reduction for each month before full retirement age: 5/9 of 1% for the first 36 months, then 5/12 of 1%.
4. Delayed retirement credit for each month after full retirement age up to 70: one twelfth of the annual rate for the year of birth (8% for 1943 and later). The credit is applied to the unreduced benefit; a claim before full retirement age earns none.
5. The earliest month of entitlement is the first month in which the person is 62 throughout: the birthday month for someone born on the 2nd, the following month for everyone else.
6. Spousal benefit: 50% of the worker's PIA at the spouse's full retirement age, reduced 25/36 of 1% for each of the first 36 months early and 5/12 of 1% beyond, never increased for delay.
7. Monthly benefit: the PIA is truncated to the dime (§415(a)(1)(A)); the reduction for early months is computed on the unreduced amount and rounded up to the dime (§402(q)(8)); delayed retirement credits add one twelfth of the annual rate per increment month (§402(w)(1)); the result is rounded down to the dollar (§415(g), before the Medicare premium the statute deducts first, which is not modeled). For any PIA that is a multiple of a dime this equals PIA × share rounded down to the dollar; a spouse's half of a PIA ending in 5 cents can come out $1 lower.
8. Timing of credits (§402(w)(3)): credits earned in the calendar year of a claim are applied from the following January, or from the month the person reaches 70 if that comes first (the statute's second clause; POMS RS 00615.690 B lists both effective months); a claim in or after the month of the 70th birthday gets every credit at once. The calculator shows the first checks separately when they differ.
9. Break-even: each month's benefit is added from the month the claim starts, and a total "by age N" includes the check for the month of the Nth birthday; each December after the earlier claim's month the PIA is raised by the COLA and truncated to the dime (§415(i)(2)(A)(ii)); every benefit received grows at the return entered, compounded monthly at the twelfth root of the annual rate on the balance received so far. The break-even month is the first month after the last one in which the earlier claim is still strictly ahead — a month in which the two totals are exactly equal counts as caught up; none is reported when the later claim never catches up by the horizon.

Not modeled: the retirement earnings test and the adjusted reduction period that follows it, survivor benefits, family maximums, dual entitlement (a spouse with a benefit of their own), the special minimum PIA, and Medicare premiums.

Taxation of benefits (IRC §86)

Calculator: Retirement withdrawal calculator

1. Provisional income = other income in AGI + tax-exempt interest + one-half of benefits, less above-the-line adjustments other than student loan interest (Publication 915, Worksheet 1, lines 1–8).
2. If it does not exceed the base amount — $25,000 single or head of household, $32,000 married filing jointly, $0 married filing separately and living together — nothing is taxable.
3. Otherwise up to 50% of the excess over the base amount is taxable, capped at half the benefits, and once provisional income passes the adjusted base amount ($34,000 / $44,000) 85% of the further excess is added, with the 50%-tier piece capped at $4,500 / $6,000; the total is capped at 85% of the benefits.
4. Married filing separately and living together: 85% of provisional income, capped at 85% of the benefits.

The engine reproduces Publication 915's four filled-in worksheets in its tests. The amounts are statutory and not indexed.

Retirement withdrawals

Calculator: Retirement withdrawal calculator

The calculator projects one year at a time: spending indexed to inflation, income that has started, the withdrawal that covers the gap after federal tax, and the balance rolled forward at the return.

1. Each year: spending = first-year spending × (1 + inflation)^{years elapsed}. Ages are the age reached in each calendar year, the way the tax rules count them.
2. Income sources that have started are added. An amount entered in today's dollars is raised by inflation for the years until it starts; after it starts it rises by its own increase (Social Security by the inflation rate, a pension by whatever you enter).
3. An income already in payment when the projection starts is entered at its current amount; its increases count from the first projected year.
4. Money kept outside the account (income above spending, or a required minimum distribution above the year's need, after tax) is spent before the account is touched; it earns the same return, untaxed.
5. The withdrawal is the amount for which income + withdrawal + outside money used − federal tax = spending, found by bisection with a bracket widened until it contains the answer.
6. Federal tax: ordinary income = the pre-tax part of the withdrawal (for a mixed account, the required minimum plus the pre-tax proportion of the rest) + pension + the taxable part of Social Security from the §86 rules above; taxable income = ordinary income − the standard deduction for the filing status, including the §63(f) additional amount for each person 65 or over, − the §151(d)(5) senior deduction (2025–2028, $6,000 per person 65 or over, each person's $6,000 less 6% of modified AGI over $75,000, or $150,000 on a joint return where both spouses' amounts are reduced, not on separate returns); the brackets and standard deduction are indexed to the projection's inflation rate each year (the §86 amounts and the senior deduction are not); tax from the 2026 brackets.
7. Required minimum distribution from the applicable age of §401(a)(9)(C)(v) (73 for births 1951–1959, 75 from 1960; a 1959 birth meets both clauses of the statute as drafted and is read as 73, as the IRS's proposed regulations do (REG-103529-23, proposed §1.401(a)(9)-2(b)(2)(v), 89 FR 58644)): the pre-tax part's opening balance ÷ the Uniform Lifetime factor for the age reached in the year (Treas. Reg. §1.401(a)(9)-5(b), (c)); the withdrawal is at least that amount, taken in the year it falls due — the option of delaying the first one to April 1 of the following year, which puts two in that year, is not modeled. The account is kept as a pre-tax part and a Roth part: the minimum comes from the pre-tax part and is taxed in full; the rest of the year's withdrawal is drawn from both in proportion to what each holds, so the pre-tax share falls only when a minimum forces more out of it.
8. The balance after the withdrawal earns the return for the year. A year in which neither the account nor the outside money can cover the spending is the year the savings run out.

Not modeled: state income tax, itemized deductions, blindness, capital-gains treatment of taxable accounts and of the outside money, Medicare premiums, variable returns.

72(t) substantially equal periodic payments (Notice 2022-6)

Calculator: 72(t) calculator

Each method converts the account balance into an annual payment: the required minimum distribution and fixed amortization methods divide by a figure from a life-expectancy table of Treas. Reg. §1.401(a)(9)-9, the fixed annuitization method by an annuity factor from its mortality rates, and the two fixed methods use an interest rate no higher than the ceiling in Notice 2022-6 §3.02(c).

1. Life expectancy from the chosen table for the owner's age on the birthday in the distribution year: the Single Life Table or the Joint and Last Survivor Table of Treas. Reg. §1.401(a)(9)-9, or the Uniform Lifetime Table as extended from age 10 in Appendix A of the Notice.
2. RMD method: payment = balance ÷ life expectancy, recomputed each year from that year's balance and age.
3. Fixed amortization: payment = balance ÷ [(1 − (1 + i)⁻ⁿ) ÷ i], n the first year's life expectancy (fractional years allowed), i the chosen rate — the IRS example's factor of 18.9559 for 36.2 years at 4% is reproduced.
4. Fixed annuitization: payment = balance ÷ Σ_k≥1 v^k·_kp_x, where v = 1/(1 + i) and _kp_x is the probability of surviving k years from the mortality rates in §1.401(a)(9)-9(e) — the IRS example's factor of 18.1568 for age 50 at 4% is reproduced. For a joint annuitization the factor pays while either life survives.
5. Rate ceiling: the greater of 5% and 120% of the federal mid-term AFR for either of the two months before the month of the first payment, read from that month's revenue ruling. The rulings print the 120% rate for four compounding periods and the Notice does not choose between them; the engine uses the annual-compounding figure. The published 120% row is the IRS's own figure (it is built from the semiannual rate, so it can differ from 1.2 × the annual AFR by up to 0.02 points) and is used as printed.
6. Modification window: the later of five years after the first payment and the day the owner reaches 59½ (birth date plus 59 years and 6 months, same day of the month, or the last day of the month when that day does not exist); the IRS's two dated examples are reproduced.

Not modeled: the recapture tax itself, the tax on the payments, the pre-2022 tables for series begun under Rev. Rul. 2002-62, transfers between plans mid-series (Notice 2022-6 §3.02(e) and §72(t)(4)(C) differ), and payments more often than annually (the annual amount may be split into installments without recomputation).

Safe withdrawal rate

Calculator: Safe withdrawal rate calculator

With real return g = (1 + r)/(1 + i) − 1 and withdrawals at the start of each of n years, the first-year rate that exhausts the portfolio at the end of year n is g ÷ [(1 + g)(1 − (1 + g)⁻ⁿ)], and 1/n when g is zero. Years remaining for a given withdrawal solve the same equation for n. A constant return is assumed throughout; the page says why that is the optimistic case.

Pension vs lump sum

Calculator: Pension vs lump sum calculator

Present value = Σ payment_t ÷ (1 + m)^t over every month t = 1, 2, … from the valuation date through the end of the horizon age, payments at the end of each month, m = (1 + r)^1/12 − 1 the monthly equivalent of the annual return, each year's payments raised by the pension's increase on the anniversary of its start (a pension already in payment enters at its current, increased amount); the required return is the rate at which that equals the lump sum (bisection); the drawdown invests the lump sum at the return and pays the same amounts until it is exhausted.

FIRE and coast FIRE

Calculator: Coast FIRE calculator · FIRE calculator

FI number = spending ÷ withdrawal rate. Years to FI solve P(1 + r)ⁿ + A((1 + r)ⁿ − 1)/r = F with contributions at the end of each year. Coast number = FI number ÷ (1 + r)^{years to retirement}; with contributions, the coast age is the first year-end at which the balance exceeds that year's coast number. Barista FI number = (spending − part-time income) ÷ withdrawal rate. Everything is in today's dollars at a real return.

How figures are verified

Each data file is read from the primary documents — SSA actuarial pages, the Internal Revenue Code, Treasury regulations, IRS notices, publications and revenue rulings — and marked verified only after a second, independent read produces the same figures and an adversarial pass has recomputed the agency's own worked examples against the calculators. The examples are pinned in automated tests; the site cannot be built while any fails. The full rules are in the editorial policy, and every dated change is on the corrections page. Tallyvane is independent developer and publisher, not a licensed financial professional or actuary; corrections to support@retirematics.com.