Open Social Security

What it is

Open Social Security is a free web calculator for one question: at what age should you, or you and your spouse, file for Social Security retirement and spousal benefits? Mike Piper, a CPA in St. Louis and author of the Oblivious Investor blog, wrote it and publishes it under the MIT licence; Brian Courts contributed the colour-coded graph of how good each filing date is. There is no account and nothing for sale.

The method is an expected present value. For a single person it assumes filing at each possible month from 62 to 70, computes the resulting annual benefit, weights each year up to age 115 by the probability of being alive, discounts that back at a real discount rate, and sums. The month with the highest present value is reported, with the value itself. Claiming dates already in the past are dropped. For a couple it adds spousal and survivor benefits, weights each year by the probability that only A, only B or both are alive, and searches every combination of both spouses' retirement and spousal filing dates.

Everything is in real, inflation-adjusted dollars. The default discount rate is the current 20-year TIPS yield, fetched from the Treasury's daily real yield curve when the page loads, with a hard-coded 1% if that request fails; you can overwrite it. Mortality defaults to the SSA period life table, roughly average health. Four Society of Actuaries 2017 CSO tables are offered for better or worse health, from non-smoker super-preferred to smoker residual standard — and you can instead enter an assumed age at death.

Inputs are the primary insurance amount from your SSA statement, date of birth, gender and marital status — single, married, divorced or widowed — plus optional situations: still working under full retirement age, which triggers the earnings test; currently on disability; children under 19 or disabled before 22; an already-filed benefit; and a possible future benefit cut. The README lists further rules it handles — deemed filing for those born before 2 January 1954, voluntary suspension, family maximum, child-in-care spousal benefits and retroactive applications.

Pricing

Free. No account and no paid tier. The About page carries an affiliate link to the author's own book on Social Security, which is the whole of its commercial side.

Data & coverage

US Social Security only. The calculator's only external data are the TIPS yield and the mortality tables; the benefit figure is the one you type in.

The README still lists the Windfall Elimination Provision and Government Pension Offset among the factors it handles. Both were repealed by the Social Security Fairness Act, signed on 5 January 2025, and the strings for them are absent from the live site's JavaScript bundle read on 4 October 2026 — so the README describes a model the site no longer runs.

Integrations

None. Inputs can be carried in the URL — the app reads PIA, dates of birth, gender, mortality table, discount rate and benefit-cut settings from query parameters — so a scenario can be shared as a link. It can also be run locally: the repository is an Angular 20 project with the standard ng serve and ng build scripts.

Limitations

• One decision only. No taxes, no accounts, no withdrawals, no spending model; it does not know whether you can afford to wait.
• Maximises expected value, not insurance. By its own author's note, a later claim that protects against a very long life can be the better choice even when it is not the top result.
• The answer is only as good as the PIA you enter — the tool does not read your earnings record, and the PIA changes with new earnings and indexing.
• No releases or changelog. Changes are commits to master; the README lags the code.
• Benefit-cut modelling is a single step at one year and one percentage, off by default.

Alternatives

MaxiFi Planner runs a Social Security optimiser inside a full lifetime plan, so a later claiming age is weighed against the gap before benefits start; its maker also sells a focused claiming tool, Maximize My Social Security. Pralana Gold and Boldin model claiming age inside a whole retirement projection, with taxes.