Sumi

A scientific calculator with the calm of ink on paper.

Sumi brings the natural display and exact arithmetic of a classic Casio fx‑991 to your phone, in an interface that gets out of the way.

Download on the App Store Get it on Google Play

Launching soon on iOS and Android.

Sumi showing the expression 2 × (3 + ½) + sin(30)² with the live result 29/4
Sumi showing sin(15°) as (√6 − √2)/4

Exact answers

Results come back as reduced fractions, surds and multiples of π, exactly as a Casio would show them. Tap S⇔D for the decimal.

Sumi's history drawer listing previous calculations

History at hand

Pull the history drawer up from the keypad to see past calculations, and tap any of them to bring the expression back for editing.

Sumi in its dark Ink theme showing 8.100000074×10⁻⁹

Paper or ink

Two quiet themes that follow your system setting, natural display editing that works the way you write, and results you can copy with a long press.

Free, with no ads and no tracking. Read the privacy policy.