Every guide here works through a real money decision with actual numbers, charts, sources and a link to the free calculator that runs the same math. A new guide is added every day. Browse by topic, or go straight to the full list of calculators.
Rent vs Buy: How Long Until Buying a Home Wins?
The honest answer to "should I rent or buy?" is a year number, not a verdict. Here is how to find yours, what drives it, and why 2026 rates stretch the break-even point.
HELOC vs Home Equity Loan: How to Choose
Both products borrow against your equity, but one gives you a lump sum at a fixed rate and the other gives you a variable-rate credit line. Here is how the payments compare, including when rates rise.
How Much Down Payment Do You Really Need for a House?
You do not need 20% to buy a home, but you do need to understand what less than 20% costs. Here are the real monthly numbers and the time it takes to save each level.
How Much Car Can I Afford? The 20/4/10 Rule With Real Numbers
The sticker price is the wrong place to start. Start with a monthly all-in transportation budget, then work backward to a price. Here is the 20/4/10 rule applied to three incomes, plus what a 72- or 84-month loan really costs.
Cash Back or Low APR? How to Pick the Better Car Deal
Manufacturers often offer "$3,000 cash back or 1.9% financing, not both." The winner depends on three numbers: the rebate, the promotional rate and the rate you can get on your own.
Compound Interest on $10,000: What It Becomes in 10, 20 and 30 Years
What does $10,000 turn into, with and without monthly contributions? Real tables for 5 to 30 years, how much compounding frequency matters, and the rule of 72.
Savings Account vs CD: Which Earns More for Your Cash?
A CD locks a rate; a savings account lets it float. Which one earns more depends on where rates go next, and whether you might need the cash. Here is the 5-year comparison under three rate paths.
How Long Does It Take to Save $1 Million?
Reaching a million is more about time and rate than income. Here are the monthly contributions needed over 20, 30 and 40 years, how long common savings amounts take, and what $1M really buys after inflation.
How Expense Ratios Quietly Cost You Six Figures
Fees are the one part of investing you can control exactly. A 1% annual fee can cost you nearly a fifth of your final balance over 30 years. Here are the numbers, and where to find your fund's costs.
ROI vs IRR vs CAGR: Which Return Number Should You Trust?
A 30% return in two years is not the same as a 150% return in twelve. Three return metrics measure different things. Here is the one-minute guide, with examples you can reproduce.
2026 401(k) and IRA Contribution Limits, Explained
Every number you need for 2026 in one place: employee limits, catch-up amounts, Roth IRA income ranges, and what the limits mean for your plan.
Roth vs Traditional 401(k) and IRA: How to Decide
The real question is whether your tax rate will be higher today or in retirement. Here is the math showing why they tie when rates match, and three situations where one pulls ahead.
How Much Do You Need to Retire? A Practical Way to Find Your Number
Forget the generic "$1 million" answer. Your number is the gap between your spending and guaranteed income, times 25. Here is the method with worked examples and its limits.
Social Security at 62 vs 67 vs 70: When Does Waiting Pay Off?
Each year you wait raises your check for life. Whether it pays depends on your health, your other income and whether you are married. Here are the monthly amounts and break-even ages.
Required Minimum Distributions: Age 73 or 75, and How to Calculate Yours
The IRS makes you start withdrawing from traditional accounts. Here is when, how to calculate the amount, what the penalty is and the legal ways to soften the tax impact.
How Much Is a $100,000 Salary After Taxes in 2026?
What actually lands in your account on $100,000? Federal tax, Social Security and Medicare, state tax and 401(k) contributions all matter. Here is the 2026 math with three state scenarios.
Hourly to Salary: What Is $25 an Hour Per Year?
The shortcut is hourly rate × 2,080. The part people miss is what changes when you take unpaid time, work overtime or compare benefits. Here is the full conversion table and the traps.
Marriage Tax Penalty or Bonus: Who Pays More in 2026?
The marriage penalty is real but narrower than people fear. Under the 2026 federal brackets, most couples pay the same or less. Here are five income combinations that show where it bites.
2026 Federal Tax Brackets and Standard Deduction, Explained With Examples
Tax brackets are not cliffs. Each rate applies only to the dollars in its band. Here are the 2026 thresholds, the standard deduction, and the difference between your marginal and effective rate.
The 50/30/20 Budget Rule: How It Works, and How to Adjust It
A budget method simple enough to use. Here are the exact dollar splits for three incomes, what counts as a need, and how to change the ratios when rent is high or you are paying off debt.
How Much Salary Do You Need to Move to a New City?
A job offer in a new city is only good or bad relative to what things cost there. Here is the simple ratio method, its limits, and how to turn it into a raise request.
How Long to Pay Off a Credit Card Making Only the Minimum?
Minimum payments are designed to keep you in debt for years. Here is the real timeline on a $6,000 balance, what a fixed payment does instead, and how to build a payoff plan.
Debt Avalanche vs Snowball: A Four-Debt Example With Real Numbers
Avalanche pays highest-rate debts first and saves the most interest. Snowball pays the smallest balance first and builds momentum. Here is a four-debt example that shows exactly how big the difference is.
Is Debt Consolidation Worth It? A $18,000 Credit Card Example
Consolidation can cut your interest dramatically or just change the shape of the problem. Here is the arithmetic for a personal loan and a 0% balance transfer, plus the red flags.