This is the third version of restone addition calculator that I made.

First version:
http://www.planetminecraft.com/project/simple-adding-calculator/

Second version:
http://www.planetminecraft.com/project/4-bit-addition-calculator/

Features:
-Doesn't use other number bases
-Night friendly as it use redstone lamp
-Calculate instantly
-Calculate up to 9 digits with maximum of 10 digits output
-Can do stacking addition

Warning:
-Maybe laggy for some computer
-Don't spam the button
-Wait for the indicator to move to press another value
-Wait for the full reset indicator to light up then you may press the numbers
-Watch my youtube video on how to use it

Update:

See update logs