Abel’s Calculators

Built by a dog, for humans

We factor in more than the others.

Most financial calculators online give you a number. We give you the full picture — modeling the real variables that shape your decisions: taxes, investment opportunity cost, equity, depreciation, break-even timing, and more. Because a decision that looks obvious on a basic calculator can look very different when the math is actually complete.

Home & Housing

Mortgage Refinance Calculator

Compare rate reductions, cash-out, and pay-down scenarios side by side — modeled as real net worth impact including equity, investments, taxes, and PMI.

Equity trajectory PMI modeling Opportunity cost

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Rent vs Buy Calculator

Should you rent or buy? Compare the true net worth impact over time — factoring in appreciation, investment opportunity cost, taxes, maintenance, and more.

Net worth comparison Tax benefits SALT cap

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Extra Payment vs Invest — Pay extra on your mortgage or invest the difference? See the net worth impact of both paths. Open → Rent or Sell Your Home — Moving out? Compare selling now (and the capital gains tax exclusion) vs. keeping it as a rental. Open →

Investing

Monte Carlo Investment Simulator

See the full range of outcomes for different asset allocations. Runs thousands of simulated futures based on historical return patterns — showing percentile bands, not just averages.

Asset allocation Fan charts Side-by-side scenarios

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Monte Carlo Withdrawal Simulator

Monte Carlo Withdrawal Simulator

Will your retirement savings last? Compare fixed, inflation-adjusted, percentage, and guardrails withdrawal strategies — stress-tested across thousands of Monte Carlo simulations with survival curves and depletion risk analysis.

4% rule Survival analysis Guardrails strategy

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FIRE Calculator — Find out when you can reach financial independence and retire early — based on your savings rate, investment returns, and target spending. Open →

Cars

Vehicle Cost of Ownership

Compare up to 3 vehicles side by side — buy new, buy used, or lease. Models depreciation, fuel, maintenance, insurance, financing, and opportunity cost.

Gas vs EV Buy vs lease Depreciation curves

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Taxes & More

Tax Bracket Visualizer — See exactly how federal income tax brackets stack — including capital gains, standard deduction, and filing status. Open → Social Security Break-Even — Should you claim at 62, 67, or 70? Model the break-even crossover and lifetime benefit under different scenarios. Open → Income & Wealth Percentile — See where your household income or net worth ranks among all Americans, with age-adjusted wealth comparisons. Open → Roth Conversion Calculator — Model the tax impact of converting traditional IRA or 401(k) funds to Roth — and see when a conversion pays off. Open → Debt Payoff Calculator — Compare snowball vs avalanche payoff strategies and see how extra payments accelerate your debt-free date. Open →

Running

Race Time Predictor — VDOT-based race time predictions adjusted for weekly mileage and course elevation. Open → Training Pace Calculator — Get your easy, tempo, interval, and race-pace zones based on a recent PR using Jack Daniels’ VDOT system. Open →

More Tools

Indian Holiday Calendar — Personalized Indian holiday calendar by religion, region, caste, and community — with descriptions and Google Calendar export. Open →

Blog

Your Income Matters Less Near Retirement

Within 5–10 years of retirement, stock market returns dwarf your contributions. The math behind Coast FIRE.

The Case Against Coast FIRE

Coast FIRE assumes median returns. In bottom-decile scenarios, continued saving is the difference between retiring and not.

Why Returns Matter More Later in Your Career

A 10% return on $50K adds $5K. On $1M it adds $100K. Why later returns have an outsized impact on your retirement date.

Pay Off Your Mortgage Early or Invest the Difference?

Should you put extra money toward your mortgage or invest it? How to compare the two paths by net worth impact.

Roth vs Traditional: When Each One Wins

The right answer depends on your tax rate now vs later. The math, plus how a Roth conversion ladder works for early retirees.

Sequence of Returns Risk in Retirement

Two portfolios with the same average return can have completely different outcomes. How sequence risk works and what to do about it.

The Best (and Worst) Cities to Be a Landlord in 2025

Cash flow, cap rates, appreciation, and tax benefits across 30 US markets. Where should rental property investors look — and which cities are a money pit?

How Monte Carlo Simulators Actually Work

Average returns are a lie. Here’s how Monte Carlo simulators model the real distribution of outcomes — and why the sequence of returns matters more than the average.

The 4% Rule: What It Gets Right (and Wrong)

The Trinity Study’s 4% rule has held up for 30 years — but sequence of returns risk, high valuations, and longer retirements mean it’s not a guarantee.

Rent vs Buy: The Real Math Most Articles Skip

Most rent vs buy comparisons ignore the opportunity cost of the down payment and the price-to-rent ratio. Here’s how to actually compare the two paths.

Gas vs Electric: What Actually Costs Less to Own?

EVs have lower running costs but higher sticker prices. The answer depends on how much you drive, where you live, and how long you keep the car.

Is Refinancing Your Mortgage Worth It?

Most refinance advice focuses on monthly savings. Here’s how to evaluate a refinance by its real impact on your net worth.

When Should You Claim Social Security?

Claiming at 62 vs 70 is a break-even math problem — but it’s also about your health, other income sources, and spouse strategy. Here’s how to think through it.

How Tax Brackets Actually Work

You don’t pay your top rate on all your income. Here’s how marginal brackets stack, why your effective rate is lower than you think, and how capital gains layer on top.

How to Build a Running Base Without Getting Injured

The 10% rule is oversimplified — and following it blindly can still get you hurt. Here’s what the research actually says about safe mileage progression.

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