How to Calculate APR (Annual Percentage Rate)
Add loan fees to the interest rate to get the true APR, with the approximation formula and a worked example.
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Explainers and guides that show the math behind our calculators.
How to Calculate an Arcana Check (D&D 5e)
Arcana check = d20 roll + Intelligence modifier + proficiency bonus (doubled with Expertise). Formula and worked example.
Read articlearrow_forwardHow to Calculate Biological Age
Estimate your biological age by scoring lifestyle habits — diet, exercise, sleep, smoking, alcohol and stress — against your calendar age.
Read articlearrow_forwardHow to Calculate the Break-Even Point
Break-even units = fixed costs ÷ (price − variable cost per unit). Formula, worked example, and how to lower your break-even.
Read articlearrow_forwardHow to Calculate Your Calorie Deficit (and the Weight You'll Lose)
The calorie deficit formula explained with a worked example, including the weekly weight loss a deficit produces and how to choose a safe target.
Read articlearrow_forwardHow to Calculate Cost of Sales (COGS)
Cost of sales = opening inventory + purchases − closing inventory. The formula with a worked example and why gross margin depends on it.
Read articlearrow_forwardHow to Calculate Credit Card Interest
Monthly credit card interest = balance × (rate ÷ 12), plus how long a fixed payment takes to clear the debt — with a worked example.
Read articlearrow_forwardHow to Calculate Dog Years
The modern dog-age approximation — 15, 9, then 4–7 per year by breed size — with a worked example and why ×7 is wrong.
Read articlearrow_forwardHow to Calculate Elevation Change from a Slope
Elevation change = distance × tan(angle) for degrees, or distance × grade ÷ 100 for percent grades. Formula and worked examples.
Read articlearrow_forwardHow to Calculate a Golf Handicap
The score differential concept and how your handicap index is built, explained in general terms with worked examples.
Read articlearrow_forwardHow to Calculate a HELOC Payment
The HELOC payment formula for interest-only and amortized payments, with a $50,000 worked example.
Read articlearrow_forwardHow to Calculate Home Equity
Home equity = home value − mortgage balance. The formula, worked example, and what you can do with your equity.
Read articlearrow_forwardHow to Calculate Inflation and Its Effect on Your Money
The inflation formula — amount × (1 + rate)^years — with a worked example showing how purchasing power erodes.
Read articlearrow_forwardHow to Calculate LTV (Loan-to-Value Ratio)
LTV = loan amount ÷ property value × 100. The formula, worked example, and what your ratio means for loan terms.
Read articlearrow_forwardHow to Calculate Macros (Protein, Fat and Carbs)
Turn your calorie target into protein, fat and carbohydrate grams — with the split formula and a worked example.
Read articlearrow_forwardHow to Calculate MAGI (Modified Adjusted Gross Income)
MAGI equals AGI plus specific add-backs like IRA contributions and student loan interest. Formula and worked example included.
Read articlearrow_forwardHow to Calculate Max Heart Rate (and Your Training Zones)
The 220−age and Tanaka max heart rate formulas explained, with a worked example and the five training zones they produce.
Read articlearrow_forwardHow to Calculate Ovulation and Your Fertile Window
Find your ovulation date as cycle length minus luteal phase, plus the 6-day fertile window — with a worked example.
Read articlearrow_forwardHow to Calculate Passive Perception (D&D 5e)
Passive Perception = 10 + Wisdom modifier + proficiency bonus (doubled with Expertise). Formula and worked examples.
Read articlearrow_forwardHow to Calculate Real GDP
Real GDP = nominal GDP ÷ GDP deflator × 100. The formula explained with a worked example and why it matters.
Read articlearrow_forwardHow to Calculate Return on Investment (ROI)
The ROI formula — profit divided by cost — plus annualized ROI, with a worked example comparing investments.
Read articlearrow_forwardHow to Calculate Ring Size
Convert finger circumference or ring diameter into US, UK and EU ring sizes, with the formula and measuring tips.
Read articlearrow_forwardHow to Calculate Roof Pitch
Roof pitch = rise ÷ run (as X-in-12), converted to degrees and percent grade. Formula and worked example included.
Read articlearrow_forwardHow to Calculate Social Security Benefits
The Social Security PIA bend-point formula explained — 90%, 32% and 15% of AIME — with a worked example.
Read articlearrow_forwardHow to Calculate TDEE (Total Daily Energy Expenditure)
Learn the TDEE formula — BMR times an activity factor — with a worked example and how to use it to lose, maintain or gain weight.
Read articlearrow_forwardHow to Calculate VO2 Max (Resting Heart Rate Method)
Estimate VO2 max with 15.3 × (max HR ÷ resting HR), plus what the numbers mean for men and women.
Read articlearrow_forwardHow to Calculate Zone 2 Heart Rate (Fat-Burn Zone)
Zone 2 heart rate is 60–70% of max HR — or 60–70% of heart-rate reserve with Karvonen. Formulas and worked examples included.
Read articlearrow_forwardBMR Explained — What Is Basal Metabolic Rate?
BMR meaning, the Mifflin-St Jeor and Katch-McArdle formulas, and how to move from BMR to your daily calorie needs.
Read articlearrow_forwardFLAMES Calculator — How the Name Game Works
The FLAMES rules explained step by step with a worked example, plus what each of the six letters stands for.
Read articlearrow_forwardHow to Calculate a Car Payment — Formula and Example
The car payment formula explained with a worked example, plus how the loan term, down payment and interest rate change your monthly cost.
Read articlearrow_forwardHow to Calculate Body Fat Percentage (US Navy Method)
The body fat formula explained with measuring instructions, category ranges and worked examples for men and women.
Read articlearrow_forwardHow to Calculate Bra Size (Band + Cup)
The two-measurement bra size method with a worked example, modern vs +4 sizing, and sister sizes explained.
Read articlearrow_forwardHow to Calculate Creatinine Clearance (Cockcroft-Gault)
The Cockcroft-Gault formula for creatinine clearance with worked examples, CKD stage categories and limitations.
Read articlearrow_forwardHow to Calculate Cubic Feet (Volume of a Box)
The volume formula, inch and centimetre conversions, and the cubic feet to liters table — with worked examples.
Read articlearrow_forwardHow to Calculate Debt to Income Ratio (DTI)
The DTI formula, what counts as debt, lender thresholds, and how to improve your ratio before a loan application.
Read articlearrow_forwardHow to Calculate Your GPA (4.0 and 10-Point Scales)
The weighted GPA formula, grade-point charts, worked examples, and the difference between GPA and CGPA.
Read articlearrow_forwardHow to Calculate Hourly Rate From Annual Salary
The hours-per-year method with worked examples, and how paid leave and overtime change your real hourly rate.
Read articlearrow_forwardHow to Calculate Hours Worked (Including Breaks & Overnight)
Clock-in to clock-out minus breaks — the simple math for a single shift, with worked examples and payroll tips.
Read articlearrow_forwardHow to Calculate Interest Rate Per Month (and Monthly Interest)
Annual to monthly rate conversion plus monthly interest on any principal, with worked examples and simple vs compound notes.
Read articlearrow_forwardHow to Calculate Your Life Path Number
The life path number formula with worked examples, the meaning of 1–9, and how master numbers 11, 22 and 33 work.
Read articlearrow_forwardHow to Calculate Maintenance Calories (BMR + Activity)
Maintenance calories explained — the BMR formula, activity multipliers, and cut/bulk targets, with a worked example.
Read articlearrow_forwardHow to Calculate Monthly Income From Any Pay Frequency
Convert hourly, weekly, biweekly or annual pay to monthly income with the simple periods-per-year method.
Read articlearrow_forwardHow to Calculate a Mortgage Payment (PITI Explained)
The mortgage payment formula — principal, interest, property tax and insurance (PITI) plus PMI — with a worked example.
Read articlearrow_forwardHow to Calculate Your Mulank (Moolank) and Bhagyank
Mulank and Bhagyank in Indian numerology explained — the formulas, the planet chart, and how to read your numbers.
Read articlearrow_forwardHow to Calculate Percentage in Excel — Formulas for Every Case
The exact Excel formulas for percent of a number, percent increase, percent change and percentage difference, with step-by-step examples.
Read articlearrow_forwardHow to Calculate Your Pregnancy Week (Gestational Age)
Pregnancy weeks explained — how to count from your last period or due date, with trimesters and a week-by-week guide.
Read articlearrow_forwardHow to Calculate Shipping Costs (UPS, USPS, FedEx)
The components of a shipping price — base rate, weight, zone and surcharges — with worked examples and money-saving tips.
Read articlearrow_forwardHow to Calculate Square Footage
The area formula for rooms, metre conversions, and material planning for flooring, paint and real estate.
Read articlearrow_forwardHow to Calculate Your Take-Home Pay (In-Hand Salary)
Gross salary to net salary step by step — standard deduction, tax slabs, cess, and new vs old regime, with worked examples.
Read articlearrow_forwardHow to Calculate a Z-Score (With Percentile)
The z-score formula explained with worked examples, normal distribution percentiles, and when z-scores are used.
Read articlearrow_forwardHow to Calculate Your Home Loan EMI (With Formula & Example)
A step-by-step guide to the EMI formula, how banks compute your monthly instalment, and how to cut total interest — with a full worked example.
Read articlearrow_forwardSIP vs FD — Which Is Better for Your Money?
A clear comparison of systematic investment plans and fixed deposits — returns, risk, taxes and the goals each suits best.
Read articlearrow_forwardCTC to In-Hand Salary — How the Conversion Works
Why your CTC is not your salary, what gets deducted (PF, professional tax, income tax) and how to compute your true take-home pay.
Read articlearrow_forwardCompound Interest Explained — The Eighth Wonder of the World
What compound interest is, how the formula works with a worked example, and why starting early beats investing more.
Read articlearrow_forwardIncome Tax Slabs 2026-27 — New vs Old Regime Explained
The latest Indian income-tax slabs, the 87A rebate, standard deduction and how to decide between the new and old regimes.
Read articlearrow_forwardBMI Explained Simply — What It Does and Doesn't Tell You
How BMI is calculated, what the categories mean, and the important limits of this popular health metric.
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