Personal finance
Savings rates, raises, interest, inflation and investment returns, with the arithmetic shown.
Personal financeHow to calculate your savings rate
Your savings rate is the money you save divided by your income, times 100. Which income to use, what counts as saving, and how to keep the number comparable over time.
Personal financeBudget percentages: the 50/30/20 split worked through
The 50/30/20 rule splits take-home pay into needs, wants and savings. How to turn it into dollar amounts, check your own split, and adjust it when the numbers don't fit.
Personal financeHow to calculate a pay raise percentage
How to calculate a raise as a percentage, your new pay after a percentage raise, hourly-to-annual conversions, and whether a raise beats inflation.
Personal financeSimple interest explained with worked examples
Simple interest is principal × rate × time. Worked examples for whole and partial years, what each variable means, and how it compares with compound interest.
Personal financeCompound interest: how percentage growth builds on itself
Compound interest pays interest on earlier interest, so growth speeds up over time. A year-by-year table, the formula, compounding frequency, and the rule of 72 with its limits.
Personal financeHow inflation shrinks purchasing power: the percentage math
When prices rise 25%, your money loses 20% of its buying power, not 25%. How to calculate purchasing power after inflation, over one year or many.
Personal financeInvestment returns: total return and annualized return (CAGR)
Total return includes price change and income; CAGR turns a multi-year return into a steady yearly rate. Why averaging yearly returns overstates growth.
Personal financeAPR vs APY: what the two percentages mean
APR is the yearly rate before compounding; APY includes compounding. How to convert APR to APY for yearly, monthly and daily compounding, and which one to compare.
Personal financeHow to calculate your debt-to-income ratio
Debt-to-income ratio is your monthly debt payments divided by your gross monthly income. What usually counts, a worked example, and how paying off one debt changes it.
Personal financePortfolio allocation percentages and how to rebalance
Work out each holding as a percentage of your portfolio, see how far it has drifted from your target, and calculate the trades needed to rebalance.