How to use the bond clean and dirty price calculator
- Enter the face value, the coupon rate and how many coupons are paid a year.
- Enter the last coupon date and the settlement date, which is when you pay for the bond.
- Enter the clean price per 100 of face value and choose the day count.
- Read the accrued interest, the dirty price per 100 and the cash due at settlement.
Formula
Coupon per period = face x coupon rate / coupons per year
Accrued interest = coupon per period x days since the last coupon / days in the coupon period
Dirty price = clean price + accrued interest per 100
30/360: each month counts as 30 days and the period is 360 / coupons per year days
Actual/actual uses real calendar days, with the period running from the last coupon to the next one.
A 6% semiannual bond with a clean price of 98.50
The last coupon was paid on June 1, 2026 and you settle on July 31. Under 30/360, 60 of the 180 days of the period have passed. The coupon is 3.00 per 100, so the accrued interest is 3.00 x 60 / 180 = 1.00 per 100, and the dirty price is 98.50 + 1.00 = 99.50.
On $1,000 of face value that is $985.00 for the bond plus $10.00 of accrued interest, $995.00 in all. Under actual/actual, the period from June 1 to December 1 is 183 days, so the accrued interest is 0.9836 and the dirty price is 99.4836.
Clean price and dirty price
Bond prices are quoted clean, without the interest that has built up since the last coupon. This keeps the quoted price from jumping up each day as interest accrues and drops at each coupon date. The buyer pays the dirty price, the clean price plus accrued interest, because the buyer will receive the whole of the next coupon and the seller must be paid for the days they held the bond.
The accrued interest is the seller's share of the coupon. If the settlement falls on a coupon date, none has accrued and the clean and dirty prices are the same.
Day counts and what this tool leaves out
Markets use different day counts. Corporate bonds often use 30/360, and government bonds often use actual/actual, but the terms of your bond decide. Holidays and month-end rules can move dates in practice. To work out the yield from a price see the Bond Yield Calculator, for interest on a loan the Accrued Interest Calculator, for price sensitivity the Bond Duration and Convexity Calculator, and for premium or discount over time the Bond Premium and Discount Amortization Calculator.
Assumptions and limits
- The coupon rate is fixed, and the next coupon date is a whole number of months after the last one.
- The settlement date is on or after the last coupon date and before the next one.
- The figures shown are examples. Use the terms and quote for your own bond.
- The tool shows the arithmetic and is not investment advice.
Frequently asked questions
Why does the dirty price differ from the quoted price?
The quote leaves out accrued interest. You pay the quote plus the interest earned since the last coupon, which is the dirty price.
What does 30/360 mean?
Each month counts as 30 days and a year as 360, so a period with two coupons a year is 180 days whatever the calendar says.
What if the settlement is after the next coupon?
The tool refuses it and names the next coupon date. Use the most recent coupon date as the last one.
Does it handle the first or last coupon period?
No. Odd first and last periods have their own rules, so this tool covers regular coupon periods only.