Ripple Carry Adder

Chain of full adders with carry propagation visualization.

Binary Inputs
= 3
= 5
Presets
Ripple Chain — 4-bit Addition
Carry
1
1
1
0
A
0
0
1
1
B
0
1
0
1
Sum
1
0
0
0
A (decimal)3
B (decimal)5
Sum (binary)1000
Sum (decimal)8
Carry Out0
Bits4
Carry Propagation — Column by Column
4
FA(0, 0, Cin=1)Sum=1 Cout=0
3
FA(0, 1, Cin=1)Sum=0 Cout=1
2
FA(1, 0, Cin=1)Sum=0 Cout=1
1
FA(1, 1, Cin=0)Sum=0 Cout=1
About the Ripple Carry Adder
A ripple carry adder chains N full adders together. The carry-out of each stage feeds into the carry-in of the next, "rippling" from the least-significant bit to the most-significant bit. While simple to understand, the propagation delay grows linearly with the number of bits — this is why real CPUs use carry-lookahead or other fast-carry techniques.