Calculators
21 of 21 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.
Amounts written out for contracts and invoices, in Russian or English.
Exact age in years, months and days, on any given date.
The arithmetic is easy; the framing is where it goes wrong
There is nothing to hide from a server here — a loan payment is not a secret. The trouble with these sums is not the calculation but calculating the wrong thing. Margin gets confused with markup, and the same inputs give two different answers. A percentage decrease gets taken against the new figure instead of the original. Stacked discounts get added when they multiply. A freelance rate gets derived from a target income with holidays and unbilled hours quietly left out.
So each calculator shows not just the answer but what it was built from, and names the trap people usually fall into beside it. It all runs in the browser — not for secrecy but so the number moves while you drag the slider, and keeps working with no network.
What is coming next
21 of the 21 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.