Money tools that show their working
Every tool here runs entirely in your browser. Nothing is uploaded, nothing is stored, and no account is needed. Each one also writes out the method and a worked example, so you can check the arithmetic rather than trust it.
-
Statement Close Optimizer
Control what your credit card reports
Your card reports its balance on the statement closing date, not the due date. Work out the exact payment, and the deadline, to report the utilization you want.
Paying by the due date changes your reported utilization by nothing.
Open the tool -
True Cost of a Purchase
The real price tag, after interest and cashback
Adds every month of interest and subtracts the cashback, so a purchase shows its actual cost and the markup you are paying over the sticker price.
A $1,200 buy at 24% APR paid at $50 a month really costs about $1,627.
Open the tool -
Tax Bracket Headroom
How far to the next federal bracket
Most calculators name your bracket. This shows how much room is left in it, what the next $1,000 costs, and how far your effective rate sits below your marginal one.
On $98,000 single, there is $23,800 of room and the next $1,000 costs $220.
Open the tool -
Loan Payment Calculator
Monthly payment and lifetime interest
Standard amortization for any fixed-rate loan, with a chart showing how much a longer term really costs in total interest.
Stretching $20,000 from 24 to 84 months adds about $7,000 of interest.
Open the tool
Why these four
There is no shortage of loan calculators on the internet. These exist because each one answers a question the standard tools skip:
- What my card reports, rather than what I owe. Utilization is scored from the statement balance, and almost every calculator models payoff instead.
- What a purchase truly costs, with interest added and cashback subtracted in the same number, instead of the two being modelled separately.
- How much room is left in my tax bracket, rather than simply naming the bracket.
- What a longer loan term really costs, in total interest rather than a lower monthly figure.
How they are built
All calculations are plain arithmetic performed in your browser: monthly amortization on a declining balance for anything involving interest, and the official 2026 IRS schedule for anything involving tax. Where a figure comes from a source, that source is linked on the page. Where a number could not be verified at its source, the feature is left out rather than estimated.
They are general education, not personalised financial advice. See our editorial policy and disclaimer.