About the Bond Accrued Interest Calculator
This bond accrued interest calculator works out how much coupon interest has built up since a bond’s last payment date, and therefore what a buyer actually pays on settlement. Enter the face value, the coupon rate and frequency, the last and next coupon dates, the settlement date, the quoted clean price and the day-count convention, and it returns the accrued interest, the days accrued and the dirty (invoice) price.
Bonds are quoted “clean”, without accrued interest, but the buyer compensates the seller for the coupon earned while the seller held the bond. That is why your trade confirmation shows a larger amount than price × face. Investors checking a confirmation, finance students and anyone comparing bonds that settle between coupon dates can use it.
The convention matters: US corporate and municipal bonds use 30/360, US Treasuries and most government bonds use Actual/Actual, and money-market instruments often use Actual/360 or Actual/365. The calculator assumes a regular coupon period (no odd first or last coupon) and that the settlement date falls between the two coupon dates.
With the default inputs, the accrued interest is $147.22. Change any value above to recalculate instantly.
How to use the bond accrued interest calculator
- 1Enter the bond’s face value, coupon rate and coupon frequency.
- 2Enter the last coupon date and the next coupon date.
- 3Enter the settlement date of your trade (usually one business day after the trade date).
- 4Pick the day-count convention from the bond’s prospectus or your broker’s quote.
- 5Enter the quoted clean price to see the dirty price you actually pay.
Formula and method
Accrued interest is the share of the next coupon that the seller has earned. Under 30/360 every month counts as 30 days and the year as 360: days = 360 × (Y2 − Y1) + 30 × (M2 − M1) + (D2 − D1), with day 31 treated as 30 (the end date only when the start date is the 30th or 31st). Actual/360 and Actual/365 count real calendar days and divide by a 360- or 365-day year.
Actual/Actual (ICMA), used for US Treasuries, divides the actual days since the last coupon by the actual days in the coupon period and multiplies by one coupon payment, so a full period always accrues exactly one coupon. The dirty or invoice price is the clean quoted price (as a percentage of par × face) plus the accrued interest.
- AI
- Accrued interest
- Days
- Days from the last coupon date to settlement under the chosen convention
- Year basis
- 360 for 30/360 and Act/360, 365 for Act/365
- Coupon payment
- Face × coupon rate ÷ coupons per year
Worked examples
$10,000 5% corporate bond, 30/360
From March 15 to July 1 is 106 days under 30/360 (4 months × 30 − 14 days). Accrued interest is $10,000 × 5% × 106 ÷ 360 = $147.22. At a clean price of 98.5 the buyer pays $9,850 + $147.22 = $9,997.22.
Same bond quoted Actual/Actual like a Treasury
There are 108 actual days from March 15 to July 1 and 184 days in the coupon period. Accrued interest is the $250 coupon × 108 ÷ 184 = $146.74, so the invoice price is $9,996.74.
Quarterly note on Actual/360
Fifty calendar days run from August 1 to September 20. On $1,000,000 at 4.2%, Actual/360 accrues $1,000,000 × 4.2% × 50 ÷ 360 = $5,833.33. Added to the $1,002,500 clean amount the buyer pays $1,008,333.33.
Frequently asked questions
What is accrued interest on a bond?+
Accrued interest is the coupon interest a bond has earned since its last payment date but not yet paid. When a bond trades between coupon dates the buyer pays it to the seller, then receives the full coupon on the next payment date.
What is the difference between clean and dirty price?+
The clean price is the quoted price without accrued interest. The dirty (full or invoice) price is the clean price plus accrued interest and is what actually changes hands at settlement. Quoting clean prices stops the price from jumping on every coupon date.
Which day-count convention should I use?+
US corporate, agency and municipal bonds usually use 30/360. US Treasury notes and bonds use Actual/Actual. Money-market instruments and many floating-rate notes use Actual/360, and some sterling and other markets use Actual/365. The bond’s offering documents state the convention.
Is accrued interest taxable?+
In the US, accrued interest you pay when buying a bond is generally not deductible as an expense; instead it reduces the taxable interest you report when you receive the next coupon. The seller reports the accrued interest received as interest income. Check IRS Publication 550 or a tax adviser for your case.
Why does 30/360 give a different number of days?+
30/360 treats every month as 30 days long, so the count ignores whether a month really has 28, 30 or 31 days. Between March 15 and July 1 it counts 106 days, while the actual calendar count is 108.
Results are estimates for educational purposes and are not financial advice. Rates, fees and terms vary — confirm with your lender or a licensed advisor before making decisions.