About Ratewit

Ratewit is a small, independent site of free money calculators, built and run by a solo developer in Bangkok.

Why it exists

Many online calculators hide how they get their numbers, ask for an email address first, or push a product. Ratewit does none of that. Each calculator shows its formula and a worked example on the same page, so you can check the math yourself, and the result updates as you type.

The site is available in English, German and Japanese. The German and Japanese pages are written natively rather than machine-translated; they have not yet been reviewed by a second native speaker.

How the calculators are tested

• One implementation. The same code produces the result shown before any JavaScript runs and the live result in your browser, so the two cannot disagree.
• Hand-checked cases on every build. Each time the site is built, known cases are recalculated and the build stops if any displayed figure is off. For the loan calculator, for example: 10,000 at 7% over 60 months must show 198.01 a month and 1,880.72 in total interest, and 3,000,000 yen at 2% over 60 months must show 52,583 yen a month and 154,997 yen in interest.
• Schedules must add up. Hundreds of loan and car loan schedules, from the shortest to the longest allowed term and from 0% to the highest allowed rate, are checked to end at a balance of exactly 0.00, or exactly at the balloon payment when there is one, with the principal repaid equal to the amount borrowed.
• Savings are checked against the textbook formula. Hundreds of compound interest runs, with monthly and yearly compounding, must match the standard future-value formula, and every year's paid-in amount plus interest must equal its balance. A fixed case: 10,000 at 5% for 10 years, compounded monthly, must show 16,470.09.
• Rounding only at the end. Totals are calculated from unrounded values and rounded only for display.
• No quoted market rates. Ratewit does not publish current interest rates or offers. Enter the figures from your own offer or contract.

Estimates, not advice

Results are estimates for planning and comparison. They are not financial advice or a loan offer. See the terms of use.

Contact

Spotted a mistake or want a new calculator? Email hello@ratewit.com.