One Calculator

A calculator that shows its working.

Every result you get stays on a tape with the expression that produced it, so a long calculation reads like a bill instead of a single number. When someone asks how you got a figure, tap Share and the whole tape goes out as a clean sheet image to WhatsApp, email or any app, with a title you choose and every step and tax note on it.

GST ON THE KEYPAD
Switch the keypad to GST mode and add or remove tax with one key. Pick 5, 12, 18 or 28 percent or type your own rate. Each line notes the CGST and SGST split, or IGST for inter-state supply. Discount and split-the-bill are one tap too. Percent works the way shops use it: 200 + 10% gives 220.

SCIENTIFIC MODE
Square, cube and nth roots, powers, logarithms, trigonometry in degrees or radians, factorial, mod, π and e, with implicit multiplication and a history you can reuse.

STUDY TOOLS, DRAWN TO YOUR NUMBERS
Circle, rectangle, triangle from three sides, trapezium, cuboid, cylinder, cone and sphere, each drawn to scale with area, volume and surface results. The unit circle with all six ratios. Quadratic equations with roots marked on the parabola. Projectile motion, Ohm's law, series and parallel resistors and uniform acceleration with their graphs. Plus a grapher for any y = f(x).

MONEY TOOLS FOR INDIA
GST calculator. Income tax under the old and new regime side by side for the current financial year, including rebate, surcharge and marginal relief. SIP, lumpsum, fixed deposit, recurring deposit and PPF projections. CTC to in-hand salary. EMI with the full repayment schedule. Rupees in words for cheques and invoices.

UNITS AND EVERYDAY HELPERS
More than 130 units in 17 categories, including square feet, square metres, gaj, bigha by state, katha, guntha, cent, marla, kanal and tola for gold. Daily reference currency rates. A formula library that calculates as you type. Percentage, discount, tip and split, and age or duration between dates.

PRIVATE BY DESIGN
No account and no sign-in. Calculations, tape and history stay on your device and are never uploaded. Only currency refresh, purchase verification and the banner in the free edition use the network. The app asks for no location, contacts, camera, microphone or storage permission.

ALSO
English and Hindi. Dark and light themes. Layouts for small phones, tablets, landscape and foldables. An Android home screen widget that shows your last answer.

FREE, WITH ONE BANNER
Every feature is included at no cost. The free edition shows a single banner on the tool screens and never a full-screen or video ad. Remove ads is a one-time purchase, not a subscription, and can be restored on your other devices. The price is shown in the app.

Results are calculations, not advice. Tax, loan and investment figures are estimates and can differ from what a bank, employer or the tax department charges. Please verify important figures independently.