Curta calculator
peterdannock • 15 May 2025 •
A former coworker of mine was a passionate calculator collector. He spent his weekends scouring garage sales and flea markets searching for vintage calculators to enhance his collection. While most of his items were electronic calculators from the 70s, 80s, and 90s, one standout piece was the world’s smallest mechanical calculator. The Curta calculator resembles a compact metal pepper grinder and can execute all four fundamental arithmetic operations: addition, subtraction, multiplication, division, and root extraction.
To perform a calculation, users enter numbers through slides (one for each digit) located on the side of the device. The revolution counter and result counter are positioned around the movable carriage at the top of the machine. A single crank turn adds the input number to the result counter at the current carriage position while increasing the corresponding digit of the revolution counter. Slightly pulling the crank upwards before turning it performs subtraction instead of addition. Users must execute a sequence of crank turns and carriage shifts for multiplication, division, and other operations. By the early 1970s, electronic calculators replaced this remarkable counting machine. They no longer manufacture calculators as they once did.
Check out this video to see how it works https://www.youtube.com/watch?v=mkSugsoFr0U
Very cool. I am familiar with this calculator, though I’ve never actually used one. I wonder if your friend has an HP 48GX, which was my go-to calculator in high school while everyone else had the TI-84.