Multiplication algorithm
（重定向自Long multiplication）
![First, set up the grid by marking its rows and columns with the numbers to be multiplied. Then, fill in the boxes with tens digits in the top triangles and units digits on the bottom.](/Images/godic/202501/24/Hindu_lattice.svg5146.png")
![Finally, sum along the diagonal tracts and carry as needed to get the answer](/Images/godic/202501/24/Hindu_lattice_2.svg5146.png")
![Demonstration of multiplying 1234 × 5678 = 7006652 using fast Fourier transforms (FFTs). Number-theoretic transforms in the integers modulo 337 are used, selecting 85 as an 8th root of unity. Base 10 is used in place of base 2w for illustrative purposes.](/Images/godic/202501/24/Integer_multiplication_by_FFT.svg5146.png")
A multiplication algorithm is an algorithm (or method) to multiply two numbers. Depending on the size of the numbers, different algorithms are in use. Efficient multiplication algorithms have existed since the advent of the decimal system.