ONE CALCULATOR
The calculator that shows its working.
Every step you type goes on a tape. GST sits right on the keypad. And when the customer asks “how did you get that?”, share the whole calculation as a clean sheet image on WhatsApp. India's first calculator built for the shop counter, the study desk and the salary slip.
Try One Calculator in your browser
These are working recreations of the app's screens. Change the numbers and watch the tape, the sheet and the diagrams update, the same way they do on your phone.
A total is not an answer. The working is.
A shopkeeper explaining a bill, a student checking a formula, a family comparing tax regimes: all of them need to see the steps, not just the last number. One Calculator keeps every step on a tape, labels the tax splits, draws the geometry, and lets you hand the whole thing to someone else as a single image.
One keypad. A drawer of tools.
The calculator is always one tap away. Everything else lives in the Tools drawer, so the keypad stays clean.
Calculator with a tape
Basic, scientific and GST modes on one keypad. Every result stays on the worksheet with its expression, so a long calculation reads like a bill.
GST on the keypad
+GST and −GST keys with 5, 12, 18 and 28% rates or your own. Each line notes the CGST/SGST or IGST split. Discount and split-the-bill are one tap too.
Share as a sheet image
Turn the tape into a titled sheet with every step, tax note and the total, and send it as a PNG to WhatsApp or email. The title is remembered for next time.
Scientific that actually works
Square, cube and nth roots, percent the way shops use it (200 + 10% = 220), powers, logs, trig in degrees or radians, factorial, mod, π and e, with implicit multiplication.
Study tools, drawn
Circles, triangles, trapeziums, cuboids, cylinders, cones, spheres, the unit circle, quadratic equations, projectile motion, Ohm's law, resistor networks and uniform acceleration, each with a diagram or graph. Plus a y = f(x) grapher.
Money tools for India
GST, old vs new income-tax regime side by side, SIP, lumpsum, FD, RD, PPF, CTC to in-hand salary, EMI with the full schedule, and rupees in words for cheques.
130+ units, Indian ones included
Square feet, square metres, gaj, bigha by state, katha, guntha, cent, marla, kanal, tola for gold, and 17 everyday categories from data to torque. Offline.
Formulas, currency, dates
A formula library where you enter values and get answers, daily reference exchange rates, percentage and discount helpers, tip and split, and age or duration between dates.
Hindi, widget and dark mode
Switch the whole app to हिन्दी. Pin your last result to the Android home screen with the widget. Dark and light themes that stay readable in a bright shop.
Your numbers stay on your phone.
There is no account, no sign-in and no analytics SDK. Your calculations, tape and shared sheets are never sent to us. The few things that do use the network are listed here, and in full in the privacy policy.
Calculations
Computed and stored only on your device. Never uploaded, never used for ads.
Sharing
The sheet image is handed straight to the app you choose. We never see it.
Currency & purchase
Exchange rates are fetched over HTTPS. Buying Remove ads sends only the store receipt to our verifier, which keeps no accounts.
Ads (free edition)
One banner from Google AdMob, requested as non-personalised, after the consent prompt for your region.
Everything is free. One banner pays for it.
No feature is locked, no trial expires and there are no subscriptions. The free edition shows a single banner on the tool screens, never on the calculator keypad, and never a full-screen ad. If you would rather not see it, Remove ads is a one-time purchase of ₹49 that you can restore on any of your devices.
One Calculator
Maison DynamicsAvailable on Google Play and the App Store in India. Store links will appear here as each listing goes live.
Built for the counter, the classroom and the kitchen table
Shopkeepers & traders
Rate × quantity, add GST, knock off a discount, and share the sheet with the customer before they ask.
Students
See the triangle, the parabola and the projectile path drawn from your own numbers, then check the formula.
Salaried & self-employed
Compare old and new tax regimes, work out in-hand salary from CTC, and plan SIPs, FDs and PPF.
Everyone else
Split a restaurant bill, convert square feet to gaj, check an EMI, or just add up the month in Hindi.
200 + 10% = 220. Not 200.1.
Many calculators get this wrong. In One Calculator, adding or subtracting a percentage works on the amount before it, so a markup or a discount is one key.
Everything you need to know
Privacy policy, terms and the support desk for One Calculator.
Privacy Policy
What stays on your device, the four features that use the network, and exactly what each one sends.
Read Privacy PolicyTerms & Conditions
Terms of use, the Remove ads purchase, and what the app does and does not promise about its results.
Read Terms & ConditionsSupport Desk
Bug reports, purchase or restore problems, a unit or formula you would like added, or a Hindi string we got wrong.
Contact Support Desk