Practical math for engineering students and investors: unit conversions, significant figures, salary and tax math, exchange rates, compound interest — with worked examples you can reproduce in the free World Calculator.
The average full-time salary in each country, run through income tax and social contributions and ranked by monthly take-home pay in USD — from the UAE and Switzerland to Vietnam and India.
2026-08-29 · 7 min read
Gross-to-net salary in South Korea for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how South Korea compares with the US, UK, Germany, Japan and Korea on the same income.
2026-08-22 · 6 min read
Gross-to-net salary in the United States for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how the United States compares with the US, UK, Germany, Japan and Korea on the same income.
2026-08-21 · 6 min read
Gross-to-net salary in Germany for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how Germany compares with the US, UK, Germany, Japan and Korea on the same income.
2026-08-20 · 6 min read
Gross-to-net salary in the United Arab Emirates for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how the United Arab Emirates compares with the US, UK, Germany, Japan and Korea on the same income.
2026-08-19 · 6 min read
Gross-to-net salary in China for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how China compares with the US, UK, Germany, Japan and Korea on the same income.
2026-08-18 · 6 min read
Gross-to-net salary in Japan for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how Japan compares with the US, UK, Germany, Japan and Korea on the same income.
2026-08-17 · 6 min read
Gross-to-net salary in the United Kingdom for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how the United Kingdom compares with the US, UK, Germany, Japan and Korea on the same income.
2026-08-16 · 6 min read
Gross-to-net salary in Canada (Ontario) for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how Canada (Ontario) compares with the US, UK, Germany, Japan and Korea on the same income.
2026-08-15 · 6 min read
Gross-to-net salary in Australia for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how Australia compares with the US, UK, Germany, Japan and Korea on the same income.
2026-08-14 · 6 min read
Gross-to-net salary in Singapore for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how Singapore compares with the US, UK, Germany, Japan and Korea on the same income.
2026-08-13 · 6 min read
Gross-to-net salary in India for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how India compares with the US, UK, Germany, Japan and Korea on the same income.
2026-08-12 · 6 min read
Gross-to-net salary in France for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how France compares with the US, UK, Germany, Japan and Korea on the same income.
2026-08-11 · 6 min read
Gross-to-net salary in Spain for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how Spain compares with the US, UK, Germany, Japan and Korea on the same income.
2026-08-10 · 6 min read
Gross-to-net salary in Italy for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how Italy compares with the US, UK, Germany, Japan and Korea on the same income.
2026-08-09 · 6 min read
Gross-to-net salary in the Netherlands for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how the Netherlands compares with the US, UK, Germany, Japan and Korea on the same income.
2026-08-08 · 6 min read
Gross-to-net salary in Sweden for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how Sweden compares with the US, UK, Germany, Japan and Korea on the same income.
2026-08-07 · 6 min read
Gross-to-net salary in Switzerland (Zurich) for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how Switzerland (Zurich) compares with the US, UK, Germany, Japan and Korea on the same income.
2026-08-06 · 6 min read
Gross-to-net salary in Saudi Arabia for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how Saudi Arabia compares with the US, UK, Germany, Japan and Korea on the same income.
2026-08-05 · 6 min read
Gross-to-net salary in Hong Kong for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how Hong Kong compares with the US, UK, Germany, Japan and Korea on the same income.
2026-08-04 · 6 min read
Gross-to-net salary in Taiwan for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how Taiwan compares with the US, UK, Germany, Japan and Korea on the same income.
2026-08-03 · 6 min read
Gross-to-net salary in Vietnam for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how Vietnam compares with the US, UK, Germany, Japan and Korea on the same income.
2026-08-02 · 6 min read
Gross-to-net salary in Thailand for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how Thailand compares with the US, UK, Germany, Japan and Korea on the same income.
2026-08-01 · 6 min read
Gross-to-net salary in the Philippines for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how the Philippines compares with the US, UK, Germany, Japan and Korea on the same income.
2026-07-31 · 6 min read
Gross-to-net salary in Indonesia for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how Indonesia compares with the US, UK, Germany, Japan and Korea on the same income.
2026-07-30 · 6 min read
Gross-to-net salary in Mexico for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how Mexico compares with the US, UK, Germany, Japan and Korea on the same income.
2026-07-29 · 6 min read
Gross-to-net salary in Brazil for five income levels: income tax, social contributions, monthly take-home pay and effective rate — plus how Brazil compares with the US, UK, Germany, Japan and Korea on the same income.
2026-07-28 · 6 min read
The same six-figure salary buys a family apartment in Riyadh, a studio in Seoul and a down payment in Sydney. Price-to-income ratios, monthly mortgage payments, and the policy levers — LTV caps, stamp duties, foreign-buyer bans — that shape each market.
2026-08-28 · 10 min read
A $5,000 international transfer can cost $12 or $280 depending on the rail you pick. The four ways money crosses borders, what each one really charges, and a one-line formula to compare any quote.
2026-08-27 · 8 min read
Six figures sounds like arrival. Run $100K through tax, a one-bedroom apartment and groceries in New York, Austin, London, Berlin, Seoul, Tokyo, Dubai and Singapore, and it ranges from "comfortable" to "roommate".
2026-08-27 · 9 min read
How compound interest actually works, why the Rule of 72 works, how compounding frequency changes the result, and the math behind "start early" — with numbers you can reproduce on any calculator.
2026-08-26 · 8 min read
A $6,250 monthly gross becomes $4,400 in the bank. Every line on an American pay stub decoded, the W-4 choices that change withholding, and the two boxes (401k match, HSA) that are free money most new hires leave unticked.
2026-08-26 · 9 min read
The rate you see on the news is not the rate you get. Learn how bank spreads, "preferential rate" discounts, card FX fees and transfer charges combine into one effective exchange rate — with formulas and a Korea-focused worked example.
2026-08-25 · 9 min read
Nobody can forecast the won. But USD/KRW is not random either: interest-rate gaps, the trade surplus, foreign stock flows, the dollar index and intervention explain most big moves. A reader's guide, with the levels that mattered in 2024–2026.
2026-08-25 · 8 min read
A $100,000 salary is not $100,000 anywhere. See how income tax, social insurance and mandatory contributions turn the same gross pay into very different monthly net amounts — and why net is not the whole story.
2026-08-24 · 10 min read
The 183-day rule is only the beginning. Tax residency tests, the double-taxation treaty tie-breaker, the US citizenship trap, digital-nomad visas and employer-of-record setups — a practical map for anyone whose paycheck crosses a border.
2026-08-24 · 9 min read
Nominal return is the number on the brochure. Real, after-tax, after-fee return is what changes your life. The exact formulas (not the shortcut), a worked example, and a table showing how a 7% return becomes 2.7%.
2026-08-23 · 8 min read
The conversions every mechanical, civil, electrical and chemical engineering student actually uses — with the dimensional-analysis method that stops you from losing a $327 million spacecraft.
2026-08-26 · 9 min read
How many digits should you report? A practical guide to sig figs, rounding, scientific notation and error propagation — with the exact rules graders check.
2026-08-25 · 8 min read
Two calculators, two answers, same keystrokes. A clear explanation of PEMDAS, implied multiplication, unary minus, and how to type expressions so every calculator agrees.
2026-08-24 · 7 min read
Typical doctoral stipends converted to monthly net pay, with the tax and social-insurance rules that make a €3,000 German contract and a $40,000 US stipend closer than they look.
2026-08-23 · 10 min read
Senior engineers catch wrong answers in seconds because they carry a dozen anchors in their head. Here they are — g, ρ of water, 1 bar, 1 hp, room temperature in three units, the speed of sound and more — with the one-line sanity check each one enables.
2026-08-23 · 7 min read