How much should you contribute to an HSA or FSA for 2027? Start from what you expect to spend on care next year, not from the IRS limit, then divide that by your paychecks. An FSA should hold only what you are sure to spend, because most of what is left at the end of the year is lost. An HSA can hold more, because the money stays yours. The last check is whether each paycheck can carry the deduction after its bills.
Why the limit is the wrong place to start
Benefits pages lead with the limit because it is the one number they are sure of. For 2027 the HSA limit is $4,500 for self only coverage and $9,000 for family coverage, set by the IRS in Revenue Procedure 2026-24. People 55 and older can add $1,000. The health FSA limit for 2027 had not been published when this was written; for 2026 it is $3,400.
A limit is a ceiling. It tells you the most the law allows, not what your paychecks can afford or what you will actually spend. Filling an FSA to the limit can mean losing money in December. Filling an HSA to the limit can mean a paycheck that no longer covers rent.
What will your medical costs be next year?
Look back before you look forward. Your last twelve months of care are the best guide you have. List what repeats:
the monthly copay times twelve
therapy, physical therapy, a specialist you see every few months
a new pair or a year of lenses
cleanings, and any filling or crown already planned
if you usually reach it, count it
Add anything you know is coming: a planned procedure, braces, a baby. Leave out the emergencies you cannot predict. Those belong in an HSA balance or an emergency fund, not in a guess. If your premium is rising too, our article on why health insurance is going up in 2027 explains that side of the bill.
Turn the election into a per paycheck figure
Your employer takes the deduction from every paycheck, so divide the year by how often you are paid. Round up to the dollar.
$47 a biweekly paycheck, $50 twice a month, $24 a week
$93 a biweekly paycheck, $100 twice a month, $47 a week
$174 a biweekly paycheck, $188 twice a month, $87 a week
The deduction comes out before income tax, so your take home pay falls by less than the deduction itself. Our guide to gross vs net pay shows where it sits on the stub.
FSA: how much can you safely put in?
Put in the costs you are sure of, and stop there. Money left in a health FSA at the end of the plan year is forfeited, unless your plan offers a small carryover or a grace period of up to two and a half months. Plans may offer one of those or neither, so read yours.
The election is also locked for the year unless you have a qualifying life event, such as a birth or a marriage. One thing works in your favour: the whole year's election is usually available from the first day of the plan year, even though it is paid off one paycheck at a time. A large bill in January can be covered by an FSA you have barely funded yet.
HSA: how much when the money rolls over?
An HSA has no deadline. What you do not spend stays in the account, moves with you if you change jobs, and is still there next year. That makes overfunding it far less risky than overfunding an FSA.
Fund at least your expected costs. If your paychecks can carry more, the HSA is a good place for it, up to the limit. Unlike an FSA election, an HSA contribution can usually be changed during the year, so you can start lower and raise it once you see how the paychecks hold up. You need a high deductible health plan to contribute at all.
Will each paycheck still cover its bills?
This is the step most people skip. Take one paycheck after the new deduction. Subtract every bill due before the next payday and what you need for groceries and gas until then. If something is still left, the election fits.
If nothing is left, lower the election before you sign it. Our guide to how much money you should have left after bills gives you a target for that number.
Doing this in Cashrou
Cashrou plans each pay period on its own. Enter your income as it really lands, after the deduction, and your bills with their due dates, and the app shows what is left between now and the next payday after the bills still to come.
Try the election before you sign it: change the income to the take home pay you expect with the new deduction and see what each pay period has left. If a medical cost you know is coming will not be covered by the account, add it as an expense in the pay period that pays it.
Cashrou has no bank connection and does not move money. Your employer makes the deduction; the app shows whether each paycheck can carry it.
