Here is a simple online Fishers LSD calculator to calculate the 'Fisher's Least Significance Difference' (LSD) on running the ANNOVA (Analysis of Variance). When you run an ANOVA (Analysis of Variance) test and get a significant result, you could notify that at least one of the groups tested differs from the other groups. To identify which group differs you run the pairwise comparison technique (comparison of two means) developed by Fisher in 1935 and is called the 'Least Significance Difference'.
The Fishers Least Significant Difference Test calculates the smallest significant between two means, just like running the test between two means instead of all the means in the group. This enables you to make direct comparisons between two means from two individual groups. Any difference larger than the LSD is considered a significant result.