Calculators
4 of 20 livePercentages, loans, margins and dates — the arithmetic you would otherwise open a spreadsheet for.
Increase, decrease, and “X is what percent of Y” in one place.
Monthly payment, total interest and the full amortisation schedule.
Add VAT or pull it back out, at any rate you need.
Days, weeks and working days between two dates.
How much a number grew, in percent and in absolute terms.
The same in the other direction, without the sign confusion.
What a regular contribution turns into, year by year.
Payment, overpayment and the effect of paying down early.
Gross to net and back, per hour, month or year.
Turn an annual figure into an honest hourly number.
Work back from a yearly target, counting holidays and downtime.
Margin and markup are not the same number. This shows both.
Price from cost, or the markup implied by a price you already set.
Return on investment, with and without the time factor.
How many units cover the fixed costs.
Final price, amount saved, and stacked discounts done right.
What a sum from one year is worth in another.
How long until a target, or how much per month to hit it.
Rates fetched daily; this one needs the network, unlike the rest.
Exact age in years, months and days, on any given date.
Why these run in the browser
Most online utilities post whatever you paste to a server and do the work there. That is fine for a toy input and a bad habit for anything else — API responses carry customer names, tokens carry credentials, and a log line carries both. Every tool in this section works with the browser's own APIs, in the tab you already have open. The practical upside is speed: no upload, no queue, no round trip, and the page keeps working with the network off. The trade-off is size — a browser tab will not chew through a 500 MB dump, so we cap the input rather than let the page freeze.
What is coming next
4 of the 20 are live today. The rest are being added in batches, and each one is listed as it lands. If a tool you need is still marked as coming and you want it sooner, say so — the order is not fixed.