The maximum pre-tax contribution dollar amount is set by law and adjusted for inflation annually. Try to contribute at least enough to qualify for your company’s maximum matching contribution. By not contributing the company’s maximum matching contribution you are leaving money on the table. Ask your Human Resources department how much you need to contribute in order to get the best match.
However, given the plans’ valuable tax breaks, it makes sense to invest the maximum if you can. There are annual limits. Check IRS.gov for changes to the annual limits.