SURVYR
PlanningHypothetical

Savings goal planner

The hypothetical contribution per period to reach a goal by a date

Open in Planner ›Carries these numbers into one plan with your other calculators.

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Hypothetical illustration only. These numbers are estimates based on your inputs and assumptions, could be completely wrong, and are not financial, investment, tax, insurance, legal, real-estate or retirement advice. Past returns don't predict future results. Important disclosures

Assumptions and limitations
  • Simulated paths draw independent lognormal monthly returns around your return setting, with a volatility preset taken from S&P 500 annual history (standard deviation of log returns). Lognormal, independent draws understate crashes, fat tails and multi-year bear markets. Simulations aren't predictions.
  • Historical paths replay actual S&P 500 sequences from every January start in the data with a complete window; they can't include futures that haven't happened, overlap heavily, and US history is one survivor among many markets.
  • The paths are 100% S&P 500 unless a stock/bond mix is offered; no other asset classes are modeled.
  • Every number is hypothetical and depends entirely on what you enter. Small changes in assumptions can change results a lot.
  • Returns are smooth and constant in the single-number projection; real returns vary every year, and real markets can do better or worse than anything shown.
  • Inflation is a single constant rate you choose (except in historical replays, which use the actual CPI of each year).
  • Growth compounds monthly (or at the contribution frequency) and contributions are made at the end of each period.
  • No taxes unless you turn on the simplified tax drag (all positive growth taxed each year at your rate, which overstates tax for buy-and-hold). No fees unless you set one.
  • Inputs stay in your browser. Saving uses this device's local storage; a share link contains the numbers you entered, so anyone with the link can see them.

S&P 500 return presets: Aswath Damodaran (NYU Stern), Historical Returns on Stocks, Bonds, Bills, Real Estate and Gold (histretSP.xls), annual S&P 500 total returns with dividends 1928-2025, compound (geometric) averages; inflation from the CPI-U (FRED CPIAUCNS) in the same file.

Historical monthly sequences: Robert J. Shiller, U.S. Stock Markets 1871-Present (ie_data.xls, shillerdata.com), monthly S&P Composite with dividends and CPI, Feb 1871 to Sep 2024. Shiller's monthly prices are averages of daily closes, which smooths month-to-month swings.

SURVYR. may be wrong. Check every number yourself, and talk to a licensed professional before acting on anything.

Coteau Planning tools are educational calculators. Coteau is not a registered investment adviser, broker-dealer, tax professional, insurance agent or other licensed professional, doesn't manage money, and doesn't sell or recommend any product. Talk to a licensed professional before making decisions. Not investment advice · Important disclosures

Generated · SURVYR. Planning · Hypothetical illustration only, not advice · survyr.app/legal/disclaimer

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Systematic research · Not investment advice · Hypothetical unless marked Live · Data: Yahoo Finance (15-min delayed), SEC EDGAR, House Clerk · Important disclosures · Contact desk@coteau.app

Coteau 0.9 · Oct 21, 2026