Bond Accrued Interest Calculator
Bond accrued interest and dirty price from coupon, dates, and day count.
What it does
Bond buyers compensate sellers for interest earned since the last coupon: the quoted clean price plus accrued interest equals the dirty price changing hands. Mid-period settlements always carry a slice.
The tool above takes face, coupon, and clean price with both dates and the day-count basis. It returns accrued with dirty price and the day fraction.
The default 6% semiannual from Jan 15 to Apr 16 accrues $15.17 over 91 of 180 days for $995.17 dirty. Par clean prices the same slice at $1,015.17.
Counting follows FINRA and MSRB rules with SEC investor pages behind them. All three agree on accrued plus clean equals dirty used here.
How to use
- Enter face value and coupon rate.
- Enter the clean quoted price.
- Pick last coupon and settlement dates.
- Pick the day-count basis.
- Read accrued first, dirty beside.
- Check the day fraction line.
Formula
- period coupon
- Face times coupon over payments per year.
- days
- Elapsed days by day-count rules.
- period
- 180 for 30/360 semiannual.
- clean
- Quoted price without interest.
Days run from the last coupon (or dated date) up to but not including settlement. Coupon-date settlements reset to $0. Actual/actual mode uses real calendar days over the real period instead of 180.
Worked example
Example: mid-period settlement
Defaults: 6% semiannual, Jan 15 to Apr 16 2025, clean $980.
- Bond: $1,000 face, 6% semiannual, clean $980.
- Period coupon: 1,000 x 6% / 2 = $30.
- Dates: Jan 15 to Apr 16, 2025.
- Days 30/360: 0 x 360 + 3 x 30 + 1 = 91 of 180.
- Accrued: 30 x 91 / 180 = $15.17.
- Dirty: 980 + 15.17 = $995.17.
- Tool shows $15.17, $995.17 dirty, 91 days of 180.
Reference table
| Bonds | Year | Period |
|---|---|---|
| Corporate / muni | 360-day | 180 semiannual |
| Treasury | Actual | 181 to 184 |
| Zero coupon | None | Clean = dirty |
| Cash trades | Trade date | Cutoff differs |
Limits
- Confirmation rounding differs slightly.
- Record-date trades adjust coupons.
- Flat and income bonds differ.
- Tax treatment sits outside.
Common mistakes
- Counting settlement day interest.
- Mixing 30/360 with actual periods.
- Forgetting coupon-date resets.
- Pricing zeros with accrual.
- Ignoring record-date deductions.
Try it yourself
Quick checks. Answers sit tucked under each question.
Clean $1,000 on defaults?
Same $15.17 slice: dirty $1,015.17.
Settlement on Jul 15 coupon date?
180 of 180 days: coupon detached, $0.00 accrued.
Defaults on actual/actual?
91 actual days over 181: 30 x 91/181 = $15.08.
Questions
How is accrued interest computed?
Coupon for the period times days elapsed over days in period. Corporate uses 30/360 day counts.
What is the dirty price?
Quoted clean price plus accrued. On coupon dates accrued resets to $0.
What is 30/360 counting?
Every month counts 30 days in a 360-day year, with month-end rules for the 31st.
What is actual/actual?
Actual calendar days with actual period length. Same dates pay slightly different accrued.
Do zero coupons accrue?
None: clean always equals dirty with no coupons to accrue.
How is accrued rounded?
Yes, with fractions of a cent at 5 mills rounding to a cent on confirmations.