Articles, explanations, & guides
Clear, accurate, plain-English explanations of the math, formulas, and decisions behind every BlinkCalc calculator. 40 guides and counting.
APR vs APY Explained: What's the Difference?
APR and APY look similar but measure interest very differently. Learn the formulas, when each is used, and how to compare loans and savings accounts correctly.
Absolute Value Explained
Absolute value strips the sign from a number, leaving only its magnitude. Learn the notation, the formal definition, and how absolute value applies in distance, error, and inequalities.
BMR vs TDEE: Understanding the Numbers Behind Your Daily Calorie Needs
BMR is what your body burns at rest. TDEE is what it burns in a real day. Learn both formulas, how activity multipliers work, and how to set calorie targets that actually fit your life.
Understanding Probability with Coin Flips and Dice Rolls
Coin flips and dice rolls are the cleanest illustrations of probability. Learn what fair random events actually look like, what they don't, and why streaks happen.
How Color Contrast Works for Accessibility
Contrast ratio determines whether text is readable. Learn how WCAG measures contrast, what passes AA and AAA, and how to fix poor contrast in your designs.
Common Financial Formulas Every Business Should Know
The financial formulas that show up most often in real business decisions: margin, ROI, break-even, NPV, working capital, and more, with worked examples.
Compound Interest Explained: How Your Money Grows Over Time
Learn how compound interest works, the formula behind it, and how compounding frequency, time, and rate change your results. Real examples, common mistakes, and FAQs.
How to Convert Cooking Measurements Accurately
From cups to grams, teaspoons to milliliters, and oven temperatures across systems. A practical reference for converting cooking measurements without ruining the recipe.
Why Cups, Grams, and Ounces Are Not Always Equal
A cup of flour and a cup of sugar weigh different amounts. Learn why volume-to-weight conversions are ingredient-specific, and how density explains it all.
Fractions, Decimals, and Percentages Explained
Three ways to express the same number. Learn how to convert between them, when each form is most useful, and the mental shortcuts that make the math fast.
Gross Profit vs Net Profit Explained
Gross profit and net profit measure two very different things on the same income statement. Learn the formulas, what's included in each, and why both matter.
What Is a Healthy Profit Margin?
A healthy profit margin depends entirely on the industry, business stage, and cost structure. Learn realistic benchmarks and how to evaluate your own margins.
HEX vs RGB vs HSL: Understanding Color Formats
Three notations for the same color, each with strengths. Learn how HEX, RGB, and HSL relate, when to use each, and how to convert between them.
How Loan Interest Is Calculated
Understand exactly how lenders compute interest on personal loans, mortgages, and auto loans. Amortization, daily accrual, and what really drives your payment.
How PDF Compression Works
PDF compression reduces file size by compressing images, fonts, and streams. Learn how lossy and lossless compression apply, and how to shrink PDFs without ruining them.
How Random Number Generators Work
Most random numbers from computers aren't truly random — they're pseudorandom, generated by deterministic algorithms. Learn the difference, how each is built, and when it matters.
How to Calculate Discounts and Sale Prices
Calculate discounts, sale prices, and the real percentage off across stacked promotions. The math behind every coupon, sale, and clearance tag.
How to Calculate Percentages: A Complete Guide With Real Examples
Master percentages once and for all. Learn the core formulas, percentage change, reverse percentages, and the mental-math shortcuts professionals use daily.
How VAT Works for Businesses and Consumers
Value-added tax is collected at every stage of production but ultimately paid by the end consumer. Learn the mechanics, the formulas, and the input/output VAT cycle.
Margin vs Markup: The Pricing Difference That Quietly Erodes Profit
Margin and markup are not the same. Learn the formulas, the conversion shortcuts, and the real-world pricing mistakes that cost businesses thousands.
Mean, Median, Mode, and Range Explained
Four measures that describe a dataset in different ways. Learn when each one tells the truth, when it lies, and how to pick the right one for the question.
Metric vs Imperial Units Explained
Two measurement systems still dominate the world. Learn the structure of each, the common conversions, and why the U.S. remains an outlier on the imperial side.
PDF vs Word vs Image Files: Which Format Should You Use?
PDFs preserve layout, Word documents stay editable, images capture pixels exactly. Learn the strengths, weaknesses, and the right format for each use case.
Percentage Increase vs Percentage Decrease Explained
Increases and decreases use different bases — that's why they don't cancel out. Learn the formulas, the recovery math, and where intuition fails.
Probability Basics: How Chance Works
Probability is the math of uncertainty. Learn the foundational rules, independent vs dependent events, conditional probability, and where intuition fails.
Ratios and Proportions Explained
Ratios compare quantities; proportions equate ratios. Learn the notation, cross-multiplication, scaling, and where ratio thinking shows up everywhere from recipes to finance.
Scientific Notation Explained With Examples
Scientific notation expresses very large or very small numbers compactly. Learn the rules, conversions, and operations, with examples from physics, biology, and finance.
Simple Interest vs Compound Interest: Key Differences
Simple interest grows in a straight line; compound interest curves upward. Learn the formulas, when each is used, and how the gap widens with time.
Standard Deviation Explained Simply
Standard deviation measures how spread out a dataset is. Learn the formula, the intuition, and how to read it in real-world contexts like grades, investments, and quality control.
How Time Zones and Time Differences Work
Time zones aren't just longitude — they're political, technical, and historical. Learn UTC, DST, offsets, and how to calculate time differences correctly.
Understanding Monthly Loan Payments
What actually determines your monthly loan payment, and how the same loan amount can produce very different payments across lenders, terms, and structures.
What Is Base64 Encoding?
Base64 turns binary data into ASCII text using 64 printable characters. Learn how it works, why it's used, and when it helps vs hurts file size.
What Is ROI and How Do You Calculate It?
ROI measures the return on an investment as a percentage of cost. Learn the formula, the limits of simple ROI, and how annualized ROI fixes the time-blindness problem.
Word Count, Character Count, and Readability Explained
How word and character counts are measured, why readability scores matter, and how to write at the right level for your audience.
Best Free Online Tools for Everyday Tasks
You don't need to install software or create an account to get things done. Here are the best free online tools for calculations, file conversions, text editing, and more, all free in your browser.
What is BMI? How to Calculate Body Mass Index Correctly
BMI is one of the most widely used health screening tools in the world, but what does your number actually mean? This guide explains the formula, the healthy range, and the limits of what BMI can tell you.
How Loan Calculators Work: Complete Beginner Guide
Loan calculators help you understand exactly what you'll pay each month and how much interest you'll pay in total. Here's everything you need to know, with clear examples.
Unix Timestamp Converter Explained With Examples
Unix timestamps are the backbone of how computers record time, from database logs to API responses. This guide explains epoch time, how to convert timestamps to dates, and when you'd need to.
What is a Good BMI? Understanding Your Results
Your BMI number means different things depending on your age, sex, and ethnicity. Here is what the ranges actually mean for your health, and when you should speak to a doctor.
How to Compare Loan Deals: APR Explained Simply
APR, interest rate, monthly payment: borrowing money comes with a lot of confusing numbers. We break it all down in plain English so you can confidently compare any loan offer.