Introduction
Accrued interest is interest that has built up but has not been paid yet. This Accrued Interest Calculator shows you how much interest has piled up on a loan or a bond, and what it costs you.
The tool has two modes:
- Loan / Debt: See how much interest grows on a student loan, personal loan, or other debt while you make no payments. This is useful during deferment or forbearance. You can also turn on capitalization to see what happens when unpaid interest gets added to your principal.
- Bond: Find the accrued interest a bond buyer owes the seller at settlement. Just enter the par value, coupon rate, coupon frequency, last coupon date, and settlement date. The calculator picks the right day-count convention for you — 30/360 for corporate and municipal bonds, Actual/Actual for Treasury bonds.
You get a clear answer, a live formula with your own numbers, step-by-step math, a chart, and a month-by-month table. No guessing and no hand math.
How to Use Our Accrued Interest Calculator
Pick a tab — Loan / Debt or Bond — then fill in your numbers. The calculator shows how much interest has built up, your new balance or the amount owed to the seller, plus a step-by-step math breakdown, chart, and table.
Loan / Debt Tab
Loan Balance: Type the amount you owe right now, before the no-payment period starts.
Annual Interest Rate: Enter the yearly rate (APR) on your loan, like 6.8 for 6.8%. If you only know your payment and term, the APR Calculator or Loan Interest Rate Calculator can back into the rate for you.
Months of No Required Payments: Enter how many whole months you can skip payments, from 1 to 99. This is your deferment or forbearance time.
Interest Payment Frequency: Choose how often you plan to pay during that time — never, monthly, quarterly, or yearly.
Voluntary Payment Amount: If you picked a payment schedule, type how much you will pay each time. This box only shows up when you choose to make payments.
Capitalize Unpaid Interest: Turn this on if your lender adds unpaid interest to your principal. That makes interest grow on a bigger balance. Leave it off if interest stays separate.
Bond Tab
Bond Type: Choose Corporate/Municipal or Government (Treasury). This sets the day-count rule for you — 30/360 or Actual/Actual.
Par / Face Value: Enter the face value of one bond, such as $1,000.
Annual Coupon Rate: Type the yearly coupon rate printed on the bond, like 5 for 5%.
Coupon Frequency: Pick how many times a year the bond pays — annual, semi-annual, quarterly, or monthly.
Last Coupon Payment Date: Enter the date of the most recent coupon paid before the trade.
Settlement Date: Enter the date the trade settles. It must come after the last coupon date. Use the Date Duration Calculator if you need to double-check the number of days between two dates.
Press Calculate to see your results, or Clear / Reset to start over.
What Is Accrued Interest?
Accrued interest is interest that has been earned but not yet paid. It builds up a little each day. On a loan, it is money you owe but have not paid yet. On a bond, it is money the bond has earned since the last coupon payment but has not paid out yet. If you want to see how interest grows over longer stretches of time, compare it with the Simple Interest Calculator and the Compound Interest Calculator.
Accrued Interest on Loans
Loans still charge interest even when you are not making payments. This happens during a student loan deferment, a forbearance, a grace period, or an interest-only period. Each month, your balance grows by a small amount of interest.
The basic math is simple:
- Monthly rate = annual rate ÷ 12
- Monthly interest = balance × monthly rate
- Total interest = monthly interest × number of months
Example: a $25,000 loan at 6.8% adds about $141.67 in interest every month. After 12 months of no payments, that is about $1,700 in extra debt. To see the same figure on a day-by-day basis, try the Daily Interest Calculator or the Monthly Interest Calculator.
What Capitalized Interest Means
Capitalizing means the unpaid interest gets added to your principal. After that, you pay interest on the interest. This makes your loan cost more. If interest is not capitalized, it sits in a separate bucket and does not grow. Once payments restart, an Amortization Calculator will show how the larger balance changes your schedule, and the Loan Interest Calculator shows the total interest over the full term.
Paying even a small amount during a no-payment period keeps the unpaid interest low. Payments go to interest first, then to principal. If you want to attack the balance faster afterward, look at the Extra Payment Calculator, the Loan Payoff Calculator, or the Debt Payoff Calculator. Credit card balances work the same way — see the Credit Card Interest Calculator.
Accrued Interest on Bonds
Bonds pay coupons on set dates, often twice a year. If you buy a bond between those dates, the seller already earned part of the next coupon. So the buyer pays the seller that share at settlement. Later, the buyer keeps the whole coupon payment.
The formula is:
Accrued Interest = Coupon Payment × (Days Accrued ÷ Days in Coupon Period)
Day-Count Conventions
Different bonds count days in different ways. This changes the answer a little.
- 30/360 — used for corporate and municipal bonds. Every month counts as 30 days and every year as 360 days.
- Actual/Actual — used for U.S. Treasury bonds. It counts the real days on the calendar.
Example: a $1,000 bond with a 5% coupon paid twice a year pays $25 per period. If 90 of the 180 days have passed, the accrued interest is $12.50.
Why Accrued Interest Matters
For borrowers, it shows the real cost of skipping payments. For bond buyers, it shows the extra cash you must pay on top of the bond price. The "clean price" is the bond price alone. The "dirty price" is the clean price plus accrued interest, and that is what you actually pay. To price the bond itself and check your return, pair this tool with the Bond Value Calculator, the Bond Yield Calculator, and the general-purpose Bond Calculator. Holders of paper series bonds can also use the Savings Bond Calculator.