NumSmith guides https://numsmith.kr/en/guides/ Mortgage, loan, compound interest, age and working-day calculators — free, no sign-up en How mortgage payments are calculated — and why the first years are almost all interest https://numsmith.kr/en/guides/how-mortgage-payments-are-calculated/ https://numsmith.kr/en/guides/how-mortgage-payments-are-calculated/ The amortization formula behind every mortgage payment, what changes when you add taxes and insurance, and how extra payments cut total interest. Tue, 22 Sep 2026 00:00:00 GMT Compound interest explained with real numbers — why starting 10 years earlier doubles the result https://numsmith.kr/en/guides/compound-interest-explained-with-real-numbers/ https://numsmith.kr/en/guides/compound-interest-explained-with-real-numbers/ How compounding actually works month by month, the rule of 72, and a side-by-side of starting at 25 versus 35 with the same monthly contribution. Tue, 22 Sep 2026 00:00:00 GMT Loan amortization schedule explained — reading the table and using it to pay off debt faster https://numsmith.kr/en/guides/loan-amortization-schedule-explained/ https://numsmith.kr/en/guides/loan-amortization-schedule-explained/ What each column in an amortization table means, how to find the balance at any month, and three ways to use the schedule to save interest. Tue, 22 Sep 2026 00:00:00 GMT Percentage change vs percentage points — the mistake that makes headlines wrong https://numsmith.kr/en/guides/percentage-change-vs-percentage-points/ https://numsmith.kr/en/guides/percentage-change-vs-percentage-points/ Why a rate going from 10 % to 15 % is both a 5-point and a 50 % increase, how to compute change correctly, and reversing a discount to find the original price. Tue, 22 Sep 2026 00:00:00 GMT BMI: what the number means, where the categories come from, and what it misses https://numsmith.kr/en/guides/bmi-what-it-means-and-what-it-misses/ https://numsmith.kr/en/guides/bmi-what-it-means-and-what-it-misses/ How BMI is calculated, the WHO cut-offs, why Asian countries use lower thresholds, and when waist size or body-fat percentage matter more. Tue, 22 Sep 2026 00:00:00 GMT How to count working days correctly for deadlines, deliveries and leave https://numsmith.kr/en/guides/how-to-count-working-days-correctly/ https://numsmith.kr/en/guides/how-to-count-working-days-correctly/ The rules that trip people up: whether day one counts, what 'five business days' means on a Friday, and which holidays to exclude. Tue, 22 Sep 2026 00:00:00 GMT How much house can I afford? The 28/36 rule, down payment and the number lenders actually use https://numsmith.kr/en/guides/how-much-house-can-i-afford/ https://numsmith.kr/en/guides/how-much-house-can-i-afford/ Turn your income into a realistic home price using debt-to-income ratios, then check the monthly cost with the mortgage calculator including taxes and insurance. Tue, 22 Sep 2026 00:00:00 GMT Exact age for forms and eligibility — how age is counted in the US, EU, Korea and Japan https://numsmith.kr/en/guides/exact-age-calculator-for-forms-and-eligibility/ https://numsmith.kr/en/guides/exact-age-calculator-for-forms-and-eligibility/ When 'age on the date of application' is measured, how Korea's 2023 age law changed things, and why some countries count age by calendar year. Tue, 22 Sep 2026 00:00:00 GMT