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Money, drafted clearly.
Nine calculators that answer specific questions in plain language: what you actually need to retire, how inflation affects your money, when to claim Social Security, Roth or traditional, how fast your debt disappears, what compounding does, where your net worth stands, and whether borrowing against your assets beats selling them.
The calculators
01
Retirement Number
Work backward from your expenses to the growth rate you actually need.
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02
Compound Interest
See your future value at every rate from 0% to 25%.
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03
Net Worth
See where your assets and debts net out, compared by age.
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04
Buy, Borrow, Die
Borrow against assets instead of selling them, risks included.
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05
Debt Payoff
See how long a balance takes to pay off, the total interest, and what an extra payment saves.
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06
Social Security Claiming Age
Compare claiming at 62, full retirement age or 70 — monthly benefit, lifetime totals and break-even ages.
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07
Roth vs. Traditional
Compare after-tax retirement value of Roth and traditional contributions at your tax rates.
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08
Inflation
What a dollar from any year since 1913 is worth today, and what today's costs will be in the future.
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09
Personal Inflation Rate
Your own inflation rate, based on how you actually spend, using the latest CPI category data.
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Where to start
Not sure which calculator to use? Most people get the most out of them in this order:
- Net Worth: see where you stand today and how you compare with households your age.
- Retirement Number: find the target your savings need to reach, based on your actual expenses.
- Compound Interest: see what your contributions can grow to, and how much the return assumption matters.
- Debt Payoff: if you carry high-interest debt, see how fast an extra payment clears it. It's often the best "return" available.
- Roth vs. Traditional and Social Security Claiming Age: fine-tune how you save and when you claim.
- Buy, Borrow, Die: if you hold appreciated assets, compare borrowing against them with selling them, risks included.
Every result is an illustration based on your assumptions, not a prediction. Our methodology page shows exactly how each calculator works.
Popular guides
Retirement
How Much Do I Need to Retire? The 4% Rule, Explained Honestly
Where the 4% rule comes from, what current research says about safe withdrawal rates, and a step-by-step way to estimate your own retirement number.
Buy, Borrow, DieBuy, Borrow, Die Explained: How the Strategy Works and Where It Breaks
A plain-English explanation of the Buy, Borrow, Die strategy: step-up in basis, borrowing against assets, a worked example, and the risks most articles skip.
Buy, Borrow, DieSecurities-Backed Lines of Credit: How They Work and the Risks to Know
How SBLOCs work, typical borrowing limits and rates, what a maintenance call is, and the questions to ask before borrowing against your portfolio.
TaxesStep-Up in Basis Explained: What Heirs Inherit and Why It Matters
How the step-up in basis works for inherited stocks and real estate, a worked tax example, community property rules, and common misconceptions.
Why Sumly
No accounts, no data collection
Every calculator runs entirely in your browser. Nothing you type is transmitted, stored, or saved anywhere — not even by us.
Plain language, real math
Every number is explained in a sentence, not just displayed. No jargon you need a glossary to get through.
Built to be honest about risk
Where a strategy has real downside — margin calls, unrealistic growth assumptions — the calculators say so plainly instead of hiding it behind an optimistic number.