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CalcIsland
Finance calculators that show the formula and the source
12 calculators: compound interest, mortgage, FIRE, DCA, FX conversion cost, Hong Kong salaries tax and MPF, US dividend withholding, and take-home pay for the US, UK, Japan and Korea. English/Traditional Chinese; formulas and official sources. Embeddable.
Hey Product Hunt 👋 I'm HY, the maker of CalcIsland.
CalcIsland is a set of free money calculators that show their working. Next to each result you'll see the formula, the assumptions, and (for tax tools) the official source and tax year it follows. Everything runs in your browser. There's no account, and nothing you type is sent to us.
A few things that make it a bit different:
• Languages: every page in English and Traditional Chinese (Hong Kong usage), plus Japanese and Korean pages for the Japan/Korea tools and core calculators
• Regional tools done carefully: Hong Kong salaries tax and MPF, US dividend withholding tax, and take-home pay for the US (2026), UK (2026/27), Japan (令和8年/2026) and Korea (2026), each checked against official worked examples
• Embeddable: put any calculator on your blog or class page with one line of code
• Short guides that explain the maths in plain language
There are 12 calculators today: compound interest, mortgage, FIRE, DCA, FX conversion cost, Hong Kong salaries tax, Hong Kong MPF, US dividend withholding tax, and US, UK, Japan and Korea take-home pay. Which tool or region should come next? And if you spot a number that looks wrong, please tell me. Accuracy matters more to me than features.
(Estimates for learning only, not financial advice.)
About CalcIsland on Product Hunt
“Finance calculators that show the formula and the source”
CalcIsland was submitted on Product Hunt and earned 0 upvotes and 1 comments, placing #98 on the daily leaderboard. 12 calculators: compound interest, mortgage, FIRE, DCA, FX conversion cost, Hong Kong salaries tax and MPF, US dividend withholding, and take-home pay for the US, UK, Japan and Korea. English/Traditional Chinese; formulas and official sources. Embeddable.
On the analytics side, CalcIsland competes within Productivity, Education and Finance — topics that collectively have 749.3k followers on Product Hunt. The dashboard above tracks how CalcIsland performed against the three products that launched closest to it on the same day.
Who hunted CalcIsland?
CalcIsland was hunted by HY. A “hunter” on Product Hunt is the community member who submits a product to the platform — uploading the images, the link, and tagging the makers behind it. Hunters typically write the first comment explaining why a product is worth attention, and their followers are notified the moment they post. Around 79% of featured launches on Product Hunt are self-hunted by their makers, but a well-known hunter still acts as a signal of quality to the rest of the community. See the full all-time top hunters leaderboard to discover who is shaping the Product Hunt ecosystem.
For a complete overview of CalcIsland including community comment highlights and product details, visit the product overview.
HY
Hey Product Hunt 👋 I'm HY, the maker of CalcIsland.
CalcIsland is a set of free money calculators that show their working. Next to each result you'll see the formula, the assumptions, and (for tax tools) the official source and tax year it follows. Everything runs in your browser. There's no account, and nothing you type is sent to us.
A few things that make it a bit different:
• Languages: every page in English and Traditional Chinese (Hong Kong usage), plus Japanese and Korean pages for the Japan/Korea tools and core calculators
• Regional tools done carefully: Hong Kong salaries tax and MPF, US dividend withholding tax, and take-home pay for the US (2026), UK (2026/27), Japan (令和8年/2026) and Korea (2026), each checked against official worked examples
• Embeddable: put any calculator on your blog or class page with one line of code
• Short guides that explain the maths in plain language
There are 12 calculators today: compound interest, mortgage, FIRE, DCA, FX conversion cost, Hong Kong salaries tax, Hong Kong MPF, US dividend withholding tax, and US, UK, Japan and Korea take-home pay. Which tool or region should come next? And if you spot a number that looks wrong, please tell me. Accuracy matters more to me than features.
(Estimates for learning only, not financial advice.)