The amount that an individual can contribute to an HSA is determined by three different factors, age, insurance type and eligibility. For people that are eligible the entire year and on the same type of insurance the entire year the contribution limits are very simple.
For someone on insurance that only covers him or herself, the contribution limit in 2017 is $3,400 and goes up to $4,400 if they are 55 or older.
For someone on insurance that covers him or herself and at least one other person, the contribution limit in 2017 is $6,750 and that goes up to $7,750 if they are 55 or older.
If a person is not eligible the entire year or their insurance type changes during the year, the limit may change. Depending on the specifics of their circumstances, figuring out the limit could be complicated. We encourage individuals to call or use the IRS worksheet to figure out their limit if they think this applies to them.
Full guidance on HSAs, including limits can be found in IRS Publication 969: http://www.irs.gov/pub/irs-pdf/p969.pdf