The contribution limits are increased over time with cost-of-living adjustments. 403(b) contribution limits are currently the same as 401(k) limits, and are adjusted for inflation at the same rate.
As of 2016, if you are under age 50, you may contribute up to $18,000. If you’re over 50, you can also make a catch-up contribution of up to $6,000, for a total of $24,000 for the year.
403(b)s also allow an additional form a catch-up for employees who have been at the job for over 15 years and whose contributions in the past average out to less than $5,000 per year. These catch-ups are called Fifteen Year Cap Expansion Option or just service-based catch-ups.
The maximum allowable additional contribution under this rule is $3,000 a year, up to $15,000 total in this “account.” These contributions can be made in addition to the regular contribution and the over-50 catch up contributions, but you should check with your plan administrator, because these contributions can be limited using a calculation that takes your contributions from other years into account.