Our Blog

Race time predictors use the Riegel formula to project a marathon or half marathon time from a recent 5K. Here's the real math, why big jumps drift, and how fall marathon training season should read the number.

Weighted grades don't average the way most students assume. Here's the exact formula for what score you need on your final exam, with a real worked example.

A pregnancy due date isn't a prediction of birth day — it's a 40-week estimate from your last period. Here's the real math behind Naegele's rule, ultrasound dating, and why the date moves.

A longer auto loan term lowers your payment but can add thousands in interest and years of negative equity. Here's the real 60- vs 84-month car loan math.

An insurance roof report and a contractor's quote can disagree by thousands of dollars in materials. Here's the roofing square math that exposes the gap before you sign anything.

What heat index actually is, how the National Weather Service calculates 'feels like' temperature, and when a hot day turns genuinely dangerous.

Summer reading lists always feel shorter than they are. Here's the real reading-time math — by word count, format, and deadline — and how to calculate your own before the bell rings.

NFL passer rating looks like a mystery number, but it's just four capped ratios averaged together. Here's the real formula, worked through with an actual draft-week argument.

The 'double your puppy's weight at 8 weeks' rule is a rough guess at best. Here's how vets actually predict adult dog size from a growth curve, worked out with real numbers.

Etsy fees quietly eat 9–15% of every sale before your own costs. Here's the real math behind Etsy profit margins, worked through with actual numbers.

Paying your full tax bill by April 15 doesn't protect freelancers from an IRS penalty. How quarterly estimated tax and the safe harbor rule actually work.

Back-to-school homework brought back the Pythagorean theorem — the same formula secretly runs TV sizing, ladder safety, and squaring a deck corner. Here's the real math.

The Perseids peak August 12–13, 2026 under a new moon — one of the darkest skies in years. Here's how moon phase controls what you'll actually see, and how to check it yourself.

Capital gains tax explained simply — short-term vs long-term rates, how cost basis actually works, tax-loss harvesting, and the mistakes that cost investors the most.

Weighted and unweighted GPA can differ by half a point on the same transcript. Here's how GPA is actually calculated, with a full worked example and a global comparison table.

VO2 max has become the wearable world's favorite longevity metric. Here's how it's actually calculated, why your watch's estimate can be off by 10 points, and a real worked example.

Why a bike tire, an aerosol can, and a bag of chips all obey PV = nRT — the ideal gas law explained through pressure and volume changes you've actually felt.

A bigger BTU number on the box doesn't guarantee a cooler room. Here's the actual BTU sizing formula, worked out against a real west-facing bedroom.

Dog food bag charts assume every dog at that weight needs the same calories. Here's the RER formula vets actually use, worked out with real numbers.

Voltage, current, and resistance explained through a genuinely hot charging cable — what Ohm's Law actually says, and how to use V = I × R without memorizing a triangle.

Batting average alone can hide a worse hitter. Here's how OBP, SLG, and OPS actually work, with a worked example showing why a .250 hitter can outproduce a .300 one.

A brown band that looked black turned a 330Ω resistor into a 33Ω one and killed my LED in half a second. Here's how 4-band and 5-band resistor color codes actually work.

Zone 2 training is everywhere right now, but most people doing it aren't actually in zone 2. Here's the real heart rate math, a worked example, and how to calculate your own zones.

Bowling scores don't just add up your pins — strikes and spares borrow points from future rolls. Here's the actual USBC scoring math, worked frame by frame.

Your pool pace per 100m almost never survives open water. Here's the real swim pace math, why open water runs slower, and how to set splits you can hit.

Punching your oven's exact temperature and time into an air fryer burns the outside before the inside finishes. Here's the real conversion math, by air fryer style.

How many drinks put you over 0.08% BAC? See the Widmark formula worked out with real numbers, why weight and sex change the answer, and why no calculator can tell you it's safe to drive.

Your treadmill's 'Fat Burn' mode is misleading you. Learn how heart rate zones actually work, the Karvonen formula vs 220-minus-age, and how to train zones 1–5 for real results.

Home EV charging costs pennies per mile — public DC fast charging is a different story. Here's the real math on EV charging costs, home vs public, and how it stacks up against gas.

A cheap 16-gauge extension cord got hot enough to smell before I understood wire gauge, amps, and voltage drop. Here's the AWG math that would have prevented it.

Splitting a group trip's costs by headcount alone almost never adds up fairly. Here's the exact math for equal splits, itemized splits, and multi-currency trips.

A turnkey rental looked like a great deal until I ran the cap rate. Learn the formula, what counts as a good cap rate in 2026, and how to avoid the same mistake.

Filling or dosing a pool without knowing its real volume wastes water, money, and chlorine. Here's the exact math for pool gallons, fill time, cost, and chlorine dosing.

The 30% federal solar tax credit ended in 2025. Here's the real math on how many panels you need and whether rooftop solar still pays for itself in 2026.

The 8-glasses-a-day rule isn't based on real science. Here's the actual formula for daily water needs — based on body weight, activity, and climate — plus how to calculate yours.

Learn how a golf handicap is really calculated under the World Handicap System, with worked examples of the score differential formula and course handicap conversion.

Most borrowers never calculate their actual student loan payoff date or total interest paid. Here's how to do it — and the strategies that can cut years off your repayment.

The SCA golden ratio is 1g of coffee per 15–18g of water — getting it right is the single biggest upgrade to home coffee. Learn the formula and the numbers for every brew method.

Most people pick their 16:8 fasting window by feel. Here's how to calculate your ideal eating window based on your sleep schedule, TDEE, and lifestyle — and why the difference matters.

Find out how much your air conditioner costs to run per hour and per month, the simple kWh formula behind every electricity bill, and which appliances really drive summer costs.

Your lunar age starts at 1 at birth and increases at Chinese New Year, not on your birthday. Learn how it is calculated and when it matters in East Asian culture.

Your one rep max unlocks every serious strength programme. Learn the Epley formula, how to estimate your 1RM safely, and how to use training percentages to actually build strength.

The 28/36 rule tells you what a bank will lend — not what you can comfortably afford. Learn how to calculate your real home affordability number before you commit.

The '3-6 months of expenses' rule is a starting point — not a formula. Learn how to calculate your real emergency fund target based on your actual situation.

Dollar-cost averaging removes emotion from investing by buying fixed amounts at regular intervals. Here's the maths behind why consistency beats market timing — every time.

Your weight tells you how much you carry. Your waist-to-hip ratio tells you where — and where matters for heart disease risk. Learn the WHO categories and how to measure correctly.

The 4% rule and 25x formula reveal your Financial Independence number. Learn how your spending — not your salary — determines when you can retire early.

Most people assume flying is their biggest carbon sin. A closer look at the numbers tells a very different story. Here's what the data actually shows.

The '1 gram per pound' rule is everywhere — but the research says something different. Learn exactly how much protein you need based on your goal, weight, and activity level.

The problem isn't how long you sleep — it's when your alarm fires. Learn the 90-minute sleep cycle formula, how to calculate your perfect bedtime, and why timing changes everything.

Learn how to calculate your TDEE, set macros for fat loss, muscle gain, or maintenance, and understand why protein is the number that matters most.

Learn exactly how to measure wall area for paint, calculate square footage for flooring and tile, apply waste factors correctly, and avoid the most costly material estimation mistakes.

The 50/30/20 rule is the simplest budgeting framework that works. Learn how to calculate your three buckets, adjust for high costs or debt, and build lasting financial habits.

Stop guessing at the hardware store. Use this simple method to calculate concrete for post holes, slabs, and footings — in metric or imperial — before you buy.

Compound interest is the most powerful force in personal finance. Learn how it works, why time matters more than amount, and how to put it to work for you today.

Self-employment tax catches freelancers and contractors off-guard every year. Learn the 15.3% rate, how to calculate your bill, and how much to set aside quarterly.

BMI is the world's most-used health metric — but most people misread it. Learn how to calculate your BMI, what the ranges mean, and why it's only part of the picture.

Learn how pace, distance, and finish time connect, how to find your easy pace, and how to use heart rate zones and calorie data to run smarter — not just harder.

Ideal weight isn't a single number — it's a range. Learn the four formulas doctors use, why BMI alone misses the mark, and what actually matters for health.

Learn how the debt avalanche and snowball methods work, which one saves more money, and how to choose the right strategy for your situation.

Learn the amortization formula behind every mortgage payment, see how rates affect your total cost, and discover what extra payments really do to your loan.