# How to quantify the error correction capacity of LDPC code?

As shown in title, I am studying the LDPC code recently. However, I still can not calculate the error correction capacity of it, maybe due to complex decoding algorithm. And there lacks easy understanding properties to infer the error correction.

An easy example is RS code (Reed solomon code). For the setting RS(N,k), while N is the block size and K is the useful symbol size. And the error correction capacity is (N-K)/2.

Is there any easy properties like RS code for LDPC code? Thanks!

As @John mentioned, there is not general way and nice formula for computing the minimum distance of codes. The problem remain difficult for LDPC codes as like as other codes. But, there are several way to construct LDPC codes, as like as finite geometry, design theory, graph theory (prototype graphs), permutation circulant matrices, random construction and other ways. Sometimes if we have more information about the method of construction of LDPC codes, we can say much more. For example, if you have QC-LDPC codes, the girth of the code (shortest cycle in the Tanner graph of code) is at most $12$ and it forces the minimum distance to have nice bound. Also, if you know that your code does not have girth $4$, and it has fixed number of $1$ (say $\lambda$) in each columns of parity check matrix, then the minimum distance is at least $\lambda +1$.