Capitalized Interest on Student Loans: What a Pause Actually Costs
Capitalized interest is unpaid interest that gets added to your student loan’s principal balance. Once it is added, it stops being “interest you owe” and becomes part of the debt itself, so it starts charging interest of its own. That is why a forbearance or deferment is not free even when no payments are due: on an illustrative $38,000 loan at 6.8% with 20 years left, a 12-month pause accrues $2,584.00 of interest, and if that interest capitalizes, the pause ends up costing $4,733.93 more over the rest of the loan than not pausing at all.
Below is what capitalization does to the balance, the formula, and worked numbers for pauses of different lengths. Whether and when your interest capitalizes is a separate question covered at the end.
What capitalized interest means, in three steps
- During the pause, interest keeps accruing. On $38,000 at 6.8%, that is $38,000 × 6.8% ÷ 12 = $215.33 a month. In the arithmetic here, it accrues on the principal only; it is tracked as a separate amount owed.
- When the pause ends, the accrued interest may be added to principal. After 12 months, $2,584.00 of interest has built up. Capitalized, the balance becomes $40,584.00.
- From then on, interest is charged on the larger balance. The $2,584.00 is now principal, so for the rest of the loan you pay interest on interest.
The formula
Interest accrued during a pause of m months:
accrued = balance × (annual rate ÷ 12) × m
The monthly payment on whatever balance P you repay over n months, with r = annual rate ÷ 12:
payment = P × r / (1 - (1 + r)^-n)
The cost of capitalization is the difference between repaying the original balance and repaying the balance plus the accrued interest. On these numbers, the payment on $38,000 over 240 months is $290.07. On $40,584.00 over the same 240 months it is $309.79 - a rise of $19.72 a month, for 240 months.
Worked example: a 12-month pause on $38,000
Here are four ways the same loan can go. Each row starts from $38,000 at 6.8% with 20 years (240 payments) of repayment remaining after the pause:
| After the pause | Monthly payment | Payments | Total paid | More than no pause |
|---|---|---|---|---|
| No pause at all | $290.07 | 240 | $69,617 | - |
| Pause; accrued interest paid before it capitalizes | $290.07 | 240 | $72,201 | $2,584.00 |
| Pause; interest capitalizes, payment recalculated | $309.79 | 240 | $74,350 | $4,733.93 |
| Pause; interest capitalizes, old payment kept | $290.07 | 279 | $80,811 | $11,194.20 |
Reading it row by row:
- Paying the accrued interest before it capitalizes costs exactly the $2,584.00 that accrued and nothing more. The balance goes back to $38,000 and the original payment resumes. Paying the $215.33 of interest each month during the pause adds up to the same $2,584.00 under this model.
- Letting it capitalize and recalculating the payment costs $4,733.93: the $2,584.00 itself plus $2,149.93 of interest on that interest. The interest on the interest is 83% of the amount that capitalized, so the pause costs 1.83 times what it accrued.
- Letting it capitalize and keeping the old payment is the costliest of the four. At $290.07, the bigger balance takes 279 payments (23 years 3 months) instead of 240, and you pay $11,194.20 more than with no pause. The extra 39 months of payments come at the end, when the original loan would already have been paid off.
All four figures assume interest on the loan stays at 6.8% and nothing else changes; the pause also pushes the end of the loan back by the length of the pause in each case.
How the cost grows with the length of the pause
Because interest accrues at the same amount every month, the cost of a pause grows in a straight line with its length:
| Pause | Interest accrued | New balance | Payment rises by | Extra paid over the term | Of which interest on interest |
|---|---|---|---|---|---|
| 3 months | $646.00 | $38,646.00 | $4.93 | $1,183.48 | $537.48 |
| 6 months | $1,292.00 | $39,292.00 | $9.86 | $2,366.96 | $1,074.96 |
| 12 months | $2,584.00 | $40,584.00 | $19.72 | $4,733.93 | $2,149.93 |
| 24 months | $5,168.00 | $43,168.00 | $39.45 | $9,467.85 | $4,299.85 |
| 36 months | $7,752.00 | $45,752.00 | $59.17 | $14,201.78 | $6,449.78 |
A three-month pause adds $1,183.48 over the term. A three-year pause accrues $7,752.00 and adds $14,201.78. Twelve times the pause, twelve times the cost.
The non-obvious part: years left matter as much as months paused
The interest on capitalized interest depends on how long that interest stays in the balance. The same 12-month pause, capitalized with different amounts of repayment still ahead:
| Years left after the pause | Interest capitalized | Payment rises by | Interest on that interest | As a share of it |
|---|---|---|---|---|
| 5 | $2,584.00 | $50.92 | $471.37 | 18% |
| 10 | $2,584.00 | $29.74 | $984.41 | 38% |
| 20 | $2,584.00 | $19.72 | $2,149.93 | 83% |
| 25 | $2,584.00 | $17.93 | $2,796.45 | 108% |
With 5 years left, the capitalized $2,584.00 costs another $471.37 in interest before it is paid off. With 25 years left it costs $2,796.45 - about 6 times as much, and more than the interest that capitalized in the first place. The monthly payment rises least in exactly the case where the total cost is highest, which is why a small change on the bill can hide a large change in the total.
This is also why paying accrued interest before it capitalizes is worth the most on a long loan: it removes the amount before it can start compounding. If you carry other debts as well, the order you pay them in is priced in debt snowball vs avalanche.
Does interest capitalize after forbearance?
It depends on the type of loan, the type of pause (forbearance, deferment, or a change of repayment plan), and the rules in force at the time. Federal rules on which events trigger capitalization have changed in recent years, and private lenders set their own terms in the loan agreement. This page does not state the current rules. To find out what applies to your loan, check studentaid.gov for federal loans, or ask your servicer directly: whether interest will capitalize when your pause ends, on what date, how much is accrued right now, and whether you can pay the accrued interest before it does.
The arithmetic above holds either way. If your accrued interest does not capitalize, your cost is closer to the “paid before it capitalizes” row; if it does, it is the recalculated or old-payment row.
One more number worth knowing on any loan: the monthly interest ($215.33 here). A payment below it does not cover the interest being charged. What happens to the shortfall - whether it is added to the balance, held separately, or treated some other way - again depends on the loan and the plan, and is a good question for your servicer.
How these were calculated
Interest during the pause accrues each month at the annual rate divided by twelve, on the principal only. When the pause ends, the accrued interest is either paid in full, or added to principal. Repayment is a standard fixed-rate amortization: each month, interest is the balance times the annual rate divided by twelve and the rest of the payment reduces principal. In the “recalculated” case the payment is re-set to clear the larger balance over the same remaining term; in the “old payment kept” case the payment is unchanged and the term runs longer, with the final month paying only what is owed. “More than no pause” is total cash paid minus the total for the same loan with no pause. Servicers may compute interest daily rather than monthly, which moves these figures slightly.
Every figure was computed twice - once by the amortization and accrual code behind the product below, and once by an independent month-by-month accrual loop and closed-form annuity formulas - and the two agree to the cent. The balance and rate are illustrative, not a quote or a typical loan, and none of this is financial advice.
If you want this run on your own balance, rate and remaining term - what a pause would add, and the payment below which your balance stops shrinking - the kit below does this arithmetic in a live workbook, with scripts for the questions to ask your servicer.