Weekly, Biweekly or Semimonthly? Splitting Annual Pay by Period
Biweekly means 26 paychecks and semimonthly means 24. Here is how to divide a salary by period, budget by month, and spot the extra-paycheck months.
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Plain-English guides to the numbers in everyday life: how a calculation works, where people go wrong, and which tool to reach for.
How Extra Payments Pay Off a Loan Faster, With Examples
Extra money sent to a loan goes straight at the balance, so the saving compounds. These worked examples show how much time and interest it can remove.
Percent Change vs Percentage Points: Why the Difference Matters
Two phrases that sound alike describe very different changes. Here is how to tell them apart, and why +25% then -20% brings you back to the start.
Percent Error Formula: How to Calculate It With Examples
Percent error tells you how far a measurement is from the accepted value, relative to that value. Here is the formula, two worked examples and the usual traps.
Permutations vs Combinations: When Does Order Matter?
Choosing 3 runners for a podium and choosing 3 people for a committee give very different counts. Learn the one question that tells you which formula to use.
Predict Your Race Time with the Riegel Formula
A 5K time can hint at your marathon time, but not by simple multiplication. The Riegel formula adds a fatigue factor, and it comes with real caveats.
Pro Rata Pay: How to Prorate a Part-Time or Partial-Year Salary
A 24-hour week on a $52,000 full-time salary is $31,200 pro rata. See the full-time-equivalent method, how leave scales, and three ways to prorate a start date.
Quick Estimation: Rounding, Benchmarks and Sanity Checks
A rough answer in your head catches most calculator mistakes. Here are practical ways to round, which benchmarks to remember and how to size the error of an estimate.
Real vs Nominal Interest Rates: Adjusting for Inflation
A 4% rate with 3% inflation does not grow your buying power by 4%. The real rate shows what is left once rising prices are taken out.
Resting Heart Rate Trends: A Simple Recovery Check
A morning pulse count costs nothing and can hint at how well you are recovering. The trick is to compare it with your own baseline, not with anyone else's.
ROI Explained: The Formula, a Worked Example and Its Limits
ROI is simple to compute and easy to misuse. This guide covers the formula, an example that compares two projects, and the traps that make ROI misleading.
Rounding Numbers: Rules, Ties and How Errors Build Up
Rounding looks trivial until a tie, a carry or a long calculation gets involved. Learn the rules, the half-up and half-even methods, and when to round.