The online tool estimate the age using the Horvath algorithm but using the Hannum's algorithm, among others. It also calculates accelerations applying some calibrations and estimate tissue and gender.
You can also do what Bryant M Schultz said, but on top of what he said, take into account as well the tissue you are studying. Hannum's signature is built from blood samples. Horvarth's signature, on the other hand, was build from a pool of multi-tissue samples.
Objective: Illumina BeadChip arrays are commonly used to generate DNA methylation data for large epidemiological studies. Updates in technology over time create challenges for data harmonization within and between studies, many of which obtained data from the older 450K and newer EPIC platforms. The pre-processing pipeline for DNA methylation is no...