DigiCalc Blog
Practical guides on finance, health, and tax calculations. Learn the methodology behind the numbers and how to use calculators effectively.
How Long Will It Take to Pay Off Credit Card Debt?
How long to pay off credit card debt? Minimum payments can take 17+ years. See the math, real examples for $5,000–$10,000 balances, and how to cut years off.
FinanceHow to Calculate Your Monthly Car Payment (Formula + Examples)
Learn the exact formula to calculate your monthly car payment, with step-by-step examples for different rates, loan terms, and down payments — plus a free calculator.
Tax & BusinessHow Do Federal Income Tax Brackets Work? (With Examples)
Federal income tax brackets are marginal — only income above each threshold is taxed at the higher rate. See how brackets work with step-by-step examples.
HealthWhat Is a Healthy BMI? How to Calculate and Interpret It
A healthy BMI falls between 18.5 and 24.9. Learn how to calculate your BMI, what the ranges mean by age and ethnicity, and where BMI falls short.
Time & DateHow Many Days Between Two Dates? (With Formula & Examples)
Calculate the exact number of days between two dates — the formula, step-by-step examples, calendar days vs business days, and a free date difference calculator.
FinanceWhat Is the 4% Rule for Retirement? Does It Still Work?
The 4% rule says withdraw 4% of your portfolio each year in retirement. Here's where it came from, how to calculate your savings target, and whether it still holds up.
Tax & BusinessHow to Calculate Payroll Taxes Step by Step
Learn how to calculate payroll taxes: Social Security, Medicare, federal withholding, and FUTA — with step-by-step examples for employees and employers.
FinanceHow to Compare Two Loan Offers and Pick the Better Deal
Comparing two loan offers? Evaluate APR, total interest, and monthly payment — step-by-step examples for mortgages, auto, and personal loans, plus a free calculator.
FinanceHow Much Should You Tip at a Restaurant? (2025 Guide)
The standard restaurant tip is 15–20%, but the right amount depends on service, establishment type, and whether you're dining in or ordering delivery. Here's the full breakdown.
FinanceWhat Is a Good Debt-to-Income Ratio? (DTI Explained)
Your debt-to-income ratio tells lenders if you can handle more debt. Learn what counts as a good DTI, how to calculate yours, and what to do if it's too high.
HealthHow to Calculate Your Pregnancy Due Date
Learn how to calculate your pregnancy due date using Naegele's Rule and the LMP method, understand trimesters, and see how ultrasound can revise your estimate.
Tax & BusinessHow to Calculate Sales Tax on Any Purchase
Learn how to calculate sales tax forward and backward — the formula, worked examples, combined local rates, exempt items, and a free sales tax calculator.
FinanceHow Does a Mortgage Amortization Schedule Work?
An amortization schedule shows exactly how each mortgage payment splits between interest and principal — and why the first years cost so much more than the last.
FinanceHow Inflation Affects the Value of Money Over Time
Inflation slowly erodes what your money can buy. See the CPI formula, real examples for $100 from 1990 to today, and how to protect your purchasing power.
FinanceHow to Calculate Return on Investment (ROI) Step by Step
Learn how to calculate return on investment (ROI) with the exact formula, step-by-step examples for stocks and real estate, and what counts as a good ROI.
HealthWhat Is a Healthy Body Fat Percentage? (By Age & Sex)
Healthy body fat percentage ranges by sex and age, how the U.S. Navy tape method works, and how body fat percentage compares to BMI — with a free calculator.
FinanceHow Much Car Can I Afford? The 20/4/10 Rule Explained
Find out how much car you can afford using the 20/4/10 rule, monthly payment math, and true ownership costs — with real examples for different incomes.
FinanceHow to Pay Off a Loan Faster (and How Much You Save)
Extra payments on a mortgage or car loan can shave years off your payoff timeline and save thousands in interest. Here's the math — with real examples.
HealthHow to Calculate Macros for Weight Loss: Step by Step
Learn exactly how to calculate your macros for weight loss — protein, carbs, and fat targets personalized to your calorie goal, with real examples.
HealthHow Much Should I Weigh for My Height? The Answer
Find your healthy weight range by height using BMI, the Hamwi formula, and Devine's method — with real examples for men and women and what the formulas can't tell you.
FinanceIs Buying an Electric Car Worth It? The Real Math
EV vs gas: real financial math on upfront cost, fuel savings, maintenance, and the $7,500 tax credit — find your actual break-even year before you buy.
HealthHow Many Calories a Day Do You Need to Lose Weight?
Find out how many calories a day you need to lose weight. Learn the TDEE formula, the 500-calorie deficit rule, and see real examples for your goal.
FinanceIs It Worth Refinancing Your Mortgage? The Break-Even Math
Find out if refinancing your mortgage makes financial sense. Calculate your break-even point, monthly savings, and total interest saved — with real examples.
FinanceIs It Cheaper to Rent or Buy a House? The Real Math
Compare the true cost of renting vs buying — mortgage, taxes, opportunity cost, and the break-even year — with real examples and a rent vs buy calculator.
FinanceIs It Cheaper to Rent or Buy a House? The Real Math
Renting vs buying isn't just about monthly payments. Compare total costs, opportunity cost, and the break-even timeline before you make the biggest financial decision of your life.
Tax & BusinessHow Much Will I Take Home After Taxes? (2025)
Estimate your 2025 take-home pay after federal income tax, Social Security, and Medicare. Real examples for $50k, $75k, and $100k salaries.
FinanceHow Much Will My Money Grow With Compound Interest?
Compound interest makes your savings snowball over time. See the formula, real-world examples, and how to calculate exactly how much your money will grow.
FinanceHow Much Will My Money Grow With Compound Interest?
See exactly how much your money will grow with compound interest. Real examples for savings, monthly contributions, and different time horizons.
Tax & BusinessHow to Calculate Your Take-Home Pay After Taxes
Learn how to calculate take-home pay after federal taxes, Social Security, Medicare, and state deductions — with a step-by-step worked example.
FinanceHow Compound Interest Grows Your Savings Over Time
See exactly how compound interest builds wealth — real dollar examples, the Rule of 72, and why starting 10 years earlier can double your final balance.
FinanceHow Much Will My Savings Grow with Compound Interest?
Learn how compound interest grows your savings over time — the formula, real dollar examples, the Rule of 72, and why starting early beats a higher rate.
Tax & BusinessHow Is Capital Gains Tax Calculated on Stocks?
Short-term vs long-term rates, cost basis methods, and step-by-step examples — everything you need to estimate your capital gains tax bill.
FinanceHow Much House Can I Actually Afford? (The Reddit-Favorite Answer)
The 28/36 rule, the true cost of homeownership, and why online calculators give you different numbers — explained plainly.
FinanceAm I On Track for Retirement? How to Check Without Panicking
A simple framework to check your retirement progress, with real numbers and the assumptions that matter most.
HealthWhy Do Calorie Calculators Give Me Different Numbers?
TDEE, BMR, Mifflin-St Jeor vs Harris-Benedict — why the same body gets different results, and which to trust.