Free financial tools

BankSync publishes a set of free financial tools at banksync.io/tools. They need no account, store nothing, and send nothing you type to a server. This page explains how they are built, because the useful thing about a calculator is whether you can check its work.

Every answer is computed before the page reaches you#

Each tool page ships a complete, correct result in its initial HTML. The number, the rate table, the methodology and the questions are all there before any JavaScript runs.

That matters for two reasons. A search engine or an AI assistant that does not execute JavaScript still sees a real answer rather than an empty shell. And if scripts fail to load, the page still answers the question it was built for — you simply cannot change the inputs.

Once the page hydrates, changing an input recomputes in the browser. Nothing is sent anywhere.

Where the rates come from#

Tools fall into two groups.

Pure arithmetic — compound interest, loan repayments, break-even, rule of 72. The maths is the same everywhere, so these are one global page with a currency selector. There is no such thing as an Australian compound interest formula, and splitting one would be padding.

Statutory — income tax, stamp duty, superannuation caps, mortgage insurance. These read from dated rule tables that record the figure, the authority it came from, and a link to the page it was published on. Every one of those sources is listed at the bottom of the tool that used it.

Rule tables are additive. A new tax year adds a file; it never edits an old one. That is what lets a page say "as at 2026-27" and mean it, and it is why a tool can still reproduce last year's answer.

A human signs off every statutory figure#

A rate table is not usable until a person has checked each value against the authority that published it and confirmed it. That confirmation is a deliberate, interactive step — it cannot be performed by a script or an automated agent, by design.

Until it happens the tool stays a draft: no page, no link, not in the sitemap. This is why the directory sometimes lists fewer tools than exist in the codebase. A calculator that is merely plausible is worse than one that is absent, because a wrong tax figure is a trust failure rather than a rounding error.

What each page shows you#

Every tool carries the same structure:

• The result, with the supporting figures that explain it.
• How this is calculated — the actual formula, and the reasoning behind the parts that catch people out.
• A worked example with real numbers you can follow end to end.
• What this assumes — stated plainly, because every calculator assumes something.
• Where this commonly goes wrong — the traps, naming the specific rule.
• Sources — the authority pages behind every statutory figure used.

There are no author bylines. The citations are the trust signal, which is why a dead link is treated as a defect rather than a cosmetic problem.

What these tools do not do#

They do not know anything about you. They are not advice, they do not account for your circumstances, and they cannot tell you what a lender or a tax authority will decide. They do arithmetic on figures you supply, using published rates, and they show their work.

For your own numbers rather than hypothetical ones, BankSync syncs your real transactions and balances into a spreadsheet, Notion, or a database — which is the difference between modelling a budget and measuring one.