Guides
The math behind the calculators
Step-by-step explanations of the formulas our tools use, with worked examples you can reproduce. Written by Kadir Laskar.
Dividends & ETFs
DRIP Compounding Explained: How Reinvested Dividends Grow
How dividend reinvestment (DRIP) compounding works step by step: share growth, yield on cost, and DRIP versus taking cash, with worked numbers.
9 min read
Yield on Cost Explained: What It Measures and What It Hides
Yield on cost explained with the formula, a year-by-year worked example, and the blind spots that make it a poor way to compare two investments.
10 min read
Monthly vs Quarterly Dividends: Does Payout Frequency Matter?
Monthly vs quarterly dividends compared with identical inputs: how much payout frequency changes compounding, budgeting and taxes, and when it does not.
10 min read
Dividend Growth vs High Yield: Which Builds More Income?
Dividend growth vs high yield investing compared with equal contributions: the break-even year, the yield-growth trade-off, and what the math ignores.
10 min read
The Dividend Crossover Point: When Dividends Out-Earn Contributions
The dividend crossover point is the year annual dividends exceed annual contributions. Learn how to calculate it, what moves it, and why it matters.
9 min read
Covered Call ETF Income: How Funds Like JEPI and JEPQ Pay
How covered call ETF income works: where option premium comes from, why payouts vary monthly, the upside you give up, and how to model JEPI and JEPQ.
9 min read
S&P 500 Index Fund Dividends: How Funds Like VOO Pay
How S&P 500 index fund dividends work: where the cash comes from, why the yield is modest, quarterly timing, reinvesting, and modeling VOO income.
9 min read
High Dividend ETFs vs Dividend Growth ETFs: How They Differ
High dividend ETFs vs dividend growth ETFs: how index rules pick stocks, why yields and growth differ, and how to model VYM, VIG and DGRO income.
9 min read
FIRE & Retirement
Coast FIRE vs Barista FIRE: The Math Behind Each Path
Coast FIRE vs Barista FIRE compared with formulas and worked examples: what each number means, how to calculate it, and how to pick your path.
9 min read
How to Calculate Your FIRE Number, Step by Step
How to calculate your FIRE number from annual spending and a withdrawal rate, then adjust it for inflation, part-time income and taxes, with examples.
10 min read
Lean FIRE vs Fat FIRE: Targets, Trade-offs and the Math
Lean FIRE vs Fat FIRE compared with the same withdrawal math: how spending sets the target, how much longer a bigger number takes, and middle paths.
9 min read
The 4% Rule and Safe Withdrawal Rates, Explained
The 4% rule and safe withdrawal rates explained: where the rule comes from, how it sets a nest egg target, and why early retirees often use less.
10 min read
Investing Math
How Accurate Is the Rule of 72? Exact Doubling Times Compared
The Rule of 72 versus the exact doubling-time formula at rates from 1% to 30%: where the shortcut is accurate, where it drifts, and why 70 also works.
9 min read
Real vs Nominal Returns: Adjusting Growth for Inflation
Real vs nominal returns explained: the Fisher equation, why subtracting inflation is only approximate, and how real returns change retirement projections.
10 min read
Averaging Down Stocks: The Math of Lowering Your Cost Basis
Averaging down stocks explained: the weighted average cost formula, how many shares hit a target average, why it gets harder, and the risks to weigh.
10 min read
How to Adjust a Dollar Amount for Inflation Using CPI
How to adjust any dollar amount for inflation using the CPI ratio formula, with worked historical examples, future cost projections and purchasing power.
10 min read
Compound Interest Explained: The Formula and Why Time Wins
Compound interest explained from the formula up: how frequency, rate and time interact, why starting early matters, and quick ways to estimate growth.
9 min read
Savings & Cash
APY vs APR: The Difference, With Conversion Formulas
APY vs APR explained: how compounding turns a stated rate into an annual yield, the exact conversion formulas, and how to compare savings accounts.
10 min read
How Much Emergency Fund Do You Need? A Practical Formula
How much emergency fund you need, worked out from essential monthly expenses and a coverage target, plus the funding gap, timeline and where to keep it.
10 min read
How a CD Ladder Works: Building One Rung by Rung
How a CD ladder works: splitting a deposit across staggered terms, rolling each rung at maturity, and the yield-versus-access trade-off, with an example.
10 min read
CD Early Withdrawal Penalties: How They Are Calculated
How CD early withdrawal penalties are calculated from months of interest, when breaking a CD can still come out ahead, and how to weigh a better rate.
9 min read
Paychecks & Work
How to Calculate Time and a Half Pay (and Double Time)
How to calculate time and a half pay: the 1.5x overtime rate, the 40-hour weekly threshold, double time, and your effective hourly rate, with examples.
9 min read
How to Calculate a Pay Raise Percentage (and What It Is Worth)
How to calculate a pay raise percentage, convert it to hourly, weekly and monthly amounts, and compare it with inflation to see what it is really worth.
9 min read
Overtime vs a Pay Raise: Which Adds More to Your Paycheck?
Overtime vs a pay raise compared on the same base pay: how many overtime hours equal a raise, why raises compound and overtime does not, and the costs.
9 min read
