781 plain-language guides to the formulas and edge cases behind our calculators.
A worked comparison of promotional financing versus a manufacturer rebate, the break-even interest rate formula, and the credit and down payment factors that change the answer.
How to compare leasing and buying by net cost and what you own at the end, including down payments, loan balances, depreciation, mileage limits, and when each approach makes sense.
How loan recasting works, a worked example with a lump-sum principal payment, how it differs from refinancing and from simply paying extra, and when each option is best.
How interest-only payments are calculated, the payment shock when amortization starts, why total cost is higher than a standard loan, and the situations in which interest-only makes sense.
How the 90-minute sleep cycle model produces suggested bedtimes, a table for common wake times, what research says about cycle length and sleep need, and tips for better sleep.
How to calculate corrected age from the due date or gestational age, a worked example with a table, when to stop correcting, and how pediatricians use it for growth and development.
How to count days, weeks, and working days to a target date, the weeks-and-days format, subtracting holidays, and planning backwards from a deadline with a checklist example.
How epoch time works, how to convert seconds to dates and back, milliseconds versus seconds, the 32-bit overflow in 2038, and examples of milestone timestamps.
The formula, a step-by-step example, a table of common triangles, a land lot application, and when the base-height method is easier.
How to compute arc length and sector area from radius and central angle, conversion between degrees and radians, segment area, and practical examples with curved edging and fan-shaped beds.
The ellipse area formula, why the perimeter is harder, three approximations compared, and examples for oval pools, tables, and garden beds.
Surface area formulas for rectangular boxes, cylinders, spheres, and cones, examples with a shipping crate, a water tank, and a duct, and tips for open tops and overlaps.
The exact formula behind UAE gratuity, straight from Article 51 of the Labour Law: 21 days per year, then 30, capped at two years' wage.
A complete numeric walkthrough of UAE gratuity for 3 years of service — simple because it never leaves the 21-day tier.
Once service passes 5 years, UAE gratuity blends two different daily rates in the same calculation — here's exactly how, with real numbers.
At long enough tenure, the standard gratuity formula would exceed the legal cap — here's a real example of exactly when that happens.
The Naismith and Tobler formulas for planning hiking time, worked examples with elevation gain, adjustments for pack weight, rest stops, and descents, and a table of common hikes.
How power-to-weight ratio determines climbing speed, how to estimate vertical ascent rate from watts per kilogram, FTP testing basics, and ways to improve the ratio.
How rowing machine pace is expressed, the Concert2 pace-to-watts conversion, a table of splits with watts and 2K times, and how to set interval paces from a 2K test.
The exponential decay formula for caffeine, a table of remaining caffeine over time, how half-life varies with genetics, pregnancy, smoking and medications, and bedtime guidelines.
How to measure and order trim, standard waste allowances, the 45 degree miter rule for square corners, a worked order for one room, and installation tips for tight corners.
Why the strip method beats square-footage estimates for wallpaper, how pattern repeat and trimming change yield per roll, a worked example, and ordering and hanging tips.
A chart matching fan diameter to room size, how to choose a downrod for ceiling height, how CFM and efficiency are measured, and tips on direction, speed, and energy savings.
How to measure countertops, avoid double counting the corner, add overhangs and waste, estimate backsplash, and compare materials like laminate, quartz, and granite by cost per square foot.
How swim pace converts to race time for common distances, how pool, wetsuit, and open-water conditions change the pace, and how to set training intervals from a time trial.
The National Weather Service wind chill and heat index formulas, tables of feels-like values, health risks at different levels, and the limits of the formulas.
How karats express purity, the troy ounce and its gram equivalent, the melt value formula with examples for several karat levels, and why resale prices are lower than spot value.
How to convert between glucose units used in different countries, the A1C to estimated average glucose formula, a conversion table, and a reminder to follow clinician targets.
Why profitable businesses run out of cash, how to set up a rolling 13-week forecast, a four-week worked table, what assumptions to use, and how to act on the results.
How to calculate DSO and read an A/R aging report, a worked example with a cash value per day, benchmarks, and practical steps for faster collections.
The three-factor DuPont identity, a worked example comparing two companies with the same ROE and very different drivers, and how to use the analysis for diagnosis and risk assessment.
How the cash conversion cycle links inventory, receivables, and payables, a worked example with cash value per day, benchmark ideas, and levers to shorten the cycle.
How readability scores are computed from sentence length and syllables, interpretation bands, a worked example, and editing tips to improve clarity.
Calculate a dog's daily calorie need with the resting energy requirement formula, convert to cups of kibble, and work out the daily and yearly cost of food at different sizes.
Calculate aquarium volume in gallons from inches, water weight and stand load, heater wattage, filter flow rate, and weekly water-change volumes for common tank sizes.
Calculate pizzas by slices per guest, estimate drinks per hour, round up for variety and leftovers, and compare per-person costs for groups of 10 to 50.
The formula for the exam score needed to reach a target course grade, worked examples at several targets and weights, and what to do when the required score is above 100%.
How to convert class rank into a percentile and top percent, a table for different class sizes, handling ties, and how rank is used in admissions and scholarships.
How to convert tuition per credit into the cost of each class, session, and hour of work, a worked example, and what the figures imply for attendance and use of resources.
Compute semesters to graduation from total credits, credits per term, and transfer credits, and estimate the full cost of taking an extra year, including tuition and lost earnings.