About JoinCalc
Free financial calculators for the US, UK, Canada and Australia
What is JoinCalc?
JoinCalc is a free set of financial calculators for people in the US, UK, Canada and Australia, covering tax, property, retirement, debt and investment questions — all built on the 2026 rates and thresholds published by the relevant tax authority.
Who runs this site
JoinCalc is built and maintained by Yunsung Nam, working from Incheon, Republic of Korea. It is an independent site — not a company, not an editorial team. There is no staff behind the word “we” anywhere on this site, and it seems more useful to say so than to imply otherwise.
An obvious question follows: why would someone in Korea build US and UK tax calculators? Because the rules these tools implement are published, precise and testable. Whether a UK salary of £110,000 attracts a 62% marginal rate is not a matter of local knowledge or opinion — it falls out of HMRC's published thresholds, and it can be checked by anyone. That is the part of this problem I can do well, and the site is deliberately limited to it.
I am not an accountant, tax adviser or financial planner.
I hold no professional financial qualification, and nothing on this site is personal advice. What this site does is narrower and, I think, more honest: it applies the rules and rates that HMRC, the IRS and other authorities publish, shows the arithmetic behind each result, and documents where every figure came from. Judging whether a result fits your circumstances is a separate question — and for anything with real financial consequences, that is a conversation to have with a qualified professional.
Why you can check the numbers yourself
Since you have no credentials of mine to rely on, the calculations are built to be verifiable instead:
- Every calculator shows a badge naming the authority its figures come from and the date they were last checked.
- The published UK and US rate tables are written from the same constants the calculators use, so a table and the tool it links to cannot disagree.
- Results are checked against a separately written implementation of the published rules before release, rather than against the code's own output.
- Known limitations are listed openly — filing status, which US states are covered, excluded local taxes — instead of being left for you to discover.
The full detail is on the How We Calculate page. If a figure looks wrong, please say so — a specific report is genuinely welcome, and corrections are made as soon as the error can be verified against the source.
Data sources
Every rate, threshold and allowance comes from the responsible authority's own published figures — not from other calculator sites — and is updated when that authority confirms a change.
🇬🇧 United Kingdom
🇦🇺 Australia
How rates are kept up to date
Tax rates change on a predictable cycle: the IRS publishes inflation adjustments in the autumn for the following January, and the UK confirms rates at fiscal events for the tax year starting 6 April. Calculators are updated when the responsible body confirms new figures — not when they are proposed or reported. Each calculator and guide carries a “✓ Checked against …” badge naming the specific body its figures are based on (HMRC, IRS, SSA, GOV.UK) and the date it was last verified, so you can judge how current a page is rather than assuming. Tools that use a standard financial formula rather than a government-set rate — loan amortisation, the 4% retirement rule — say so directly instead of citing an authority that does not apply.
Important Disclaimer
⚠️ For informational purposes only
JoinCalc calculators provide estimates based on standard tax rules and publicly available rates. They do not constitute financial, tax, or legal advice, and are not produced by a qualified professional. Individual circumstances vary and tax situations can be complex — always consult a qualified financial adviser, tax professional or solicitor before making significant financial decisions.
Results may differ from your actual liability because of personal allowances, deductions, exemptions, local taxes or legislative changes the calculators do not model. The known limitations are listed in full on the How We Calculate page.
How the site is funded
JoinCalc is funded by advertising. Every calculator is free, there is no premium tier, no account and no paywall, and no lead or mailing list is ever sold — none of which would be possible anyway, since calculations run entirely in your browser and your numbers are never transmitted or stored. Advertising is separate from the calculations: no result, ranking or comparison on this site is influenced by an advertiser. Where a page concludes that one option costs less than another, that comes from the arithmetic on the page and nothing else.
Contact and corrections
Found a figure that looks wrong, or want a calculator that does not exist yet? Please get in touch. A calculator is only worth using if it is accurate, so corrections are taken seriously and made as soon as the error can be verified against the source. The most useful reports name the page, the inputs you used and the result you expected.
Contact Us