Retire Slider

What is Retire Slider?

Retire Slider is a stripped-down retirement planner for people who don't want to fill out a 40-field questionnaire before they get a number. Type in your net worth, slide your annual spending up or down, and the app shows your 30-year risk of ruin — the probability your portfolio hits zero within the next three decades — recomputed instantly as you drag. Social Security, a rough expense breakdown, and federal + state taxes are all folded in.

How it works

• Enter your net worth, expected real return (default 5% after inflation), and monthly Social Security income
• Slide your total annual spending — the risk-of-ruin number updates as you drag
• Open the expense breakdown to enter fixed costs: Medicare, mortgage or rent, home insurance, property taxes, maintenance
• Click Estimate taxes to auto-fill federal and state income tax based on your withdrawal and 85% of Social Security
• Run a 25,000-path Monte Carlo cross-check with one click to sanity-check the closed-form estimate
• Hit Copy shareable link to send the exact scenario to another device or another person — state travels in the URL, not on a server

Closed-form, not simulated

Most retirement calculators run Monte Carlo simulations under the hood, which means the number wiggles a little every time you touch a slider. Retire Slider uses a closed-form reciprocal-gamma approximation (Milevsky & Robinson) instead: it treats the stochastic present value of your shortfall stream as an inverse-gamma distribution matched to its exact mean and variance under geometric Brownian motion, and evaluates a single Gamma CDF to get ruin probability.

• Zero simulation noise — the number is deterministic for a given set of inputs
• Fast enough to update while you drag a slider, not after you release it
• Real returns throughout — every dollar you type is in today's purchasing power
• Optional Monte Carlo cross-check confirms the closed-form and simulation agree to within ~±0.3%

Assumptions

• Horizon: 30 years. Ruin means the invested balance hits $0 within that window
• Expected real return: user-controlled slider, 0–10% (default 5%), with 15% annualized volatility — roughly a diversified stock-heavy portfolio
• Social Security: a constant real annuity that offsets total spending; the portfolio only funds the shortfall (total spending − SS)
• Taxes: conservative estimate — federal ordinary-income brackets on withdrawal + 85% of SS, state rate applied to the same base, held constant in real terms
• Expenses: total spending = household spending (slider) + fixed expenses; all in today's dollars

This is a rough teaching tool for exploring how spending, returns, and Social Security trade off against risk. It is not personalized financial advice. For a full plan with multi-account tax strategy, Roth conversion timing, and the “widow tax” on survivor spouses, use Monaco.

Privacy

• Everything runs in your browser — net worth, spending, and Social Security never leave your device
• Inputs persist in local storage so the page opens where you left off; clear your browser storage to wipe them
• Shareable links encode the scenario in the URL fragment (after the #), which browsers never send to servers or logs
• No accounts, no analytics, no advertising trackers

Retire Slider has its own dedicated policy separate from the Yellow Sun Systems LLC umbrella — see the Retire Slider Privacy Policy for the full terms.