Bond Accrued Interest Calculator
Accrued interest on a bond between coupon dates under 30/360, 30E/360, actual/actual (ICMA or ISDA), actual/365 and actual/360. Start from the last coupon date or from the maturity date, and get the dirty price from a clean price or from a yield, the yield from a clean price, every convention side by side, and the worked steps.
How it works
Accrued = coupon per period × accrued days ÷ days in the period 30/360: days = 360 × (Y2 − Y1) + 30 × (M2 − M1) + (D2 − D1), with day 31 (and end-of-February on month-end bonds) treated as 30; period = 360 ÷ coupons a year · 30E/360: every day 31 becomes 30 Actual/Actual (ICMA): actual days ÷ actual days in the coupon period · Actual/Actual ISDA: annual coupon × (days in non-leap years ÷ 365 + days in leap years ÷ 366) Actual/365: annual coupon × actual days ÷ 365 · Actual/360: annual coupon × actual days ÷ 360 Dirty price = clean price + accrued · From a yield y: dirty = Σ c ÷ (1 + y/m)^(k − 1 + DSC/E) + 100 ÷ (1 + y/m)^(N − 1 + DSC/E)
Bond interest builds up every day but is paid in lumps, so when a bond changes hands between coupon dates the buyer pays the seller the interest earned since the last payment. That accrued interest is added to the quoted clean price, and the total is the dirty or invoice price. The buyer then receives the whole next coupon, so the seller ends up with the interest for the days they held the bond. How the days are counted is set by the bond’s day-count convention. US Treasuries use actual days over the actual length of the coupon period. US corporate, agency and municipal bonds use 30/360, which treats every month as 30 days. Eurobonds use the European 30E/360 variant. Money-market instruments use actual/360, some sterling and Canadian bonds use actual/365, and swaps and some notes use actual/actual ISDA, which splits the days by calendar year. The table shows the same trade under all six so you can see how much the convention matters — usually a few cents to a few dollars on $10,000. You can start from the last coupon date, or give the maturity date and let the calculator build the coupon schedule, count the coupons left and price the bond from a yield. With a maturity date and a clean price it also solves the yield to maturity.
Worked example
A $10,000 bond with a 5% semi-annual coupon last paid on June 15, settling on September 26, actual/actual: 103 of the 183 days in the period have passed, so accrued interest is $250 × 103 ÷ 183 = $140.71 (1.4071 per 100). At a clean price of 98.50 the invoice price is 99.9071, or $9,990.71. Under 30/360 the same trade counts 101 of 180 days, for $140.28. A 5.75% bond maturing on November 15, 2017, bought on February 15, 2008 at a 6.5% yield on 30/360, prices at 94.6344 clean, with 1.4375 of accrued interest.
Sources: MSRB Rule G-33 — Calculations (30/360 day count for municipal securities) · Microsoft — PRICE function (settlement, maturity, rate, yield, basis)
Frequently asked questions
Why does 30/360 give a different number?
Because it treats every month as 30 days. From June 15 to September 26 it counts 101 days out of 180, while actual/actual counts 103 out of 183. The difference is usually small, but the trade settles on the bond’s own convention, so use the one in its prospectus or on your trade confirmation.
Do I pay tax on accrued interest I paid the seller?
In the US, no. You report the full coupon you receive and subtract the accrued interest you paid (on Schedule B), and the seller reports it as income. Other countries have their own rules, such as the UK’s accrued income scheme, so check locally.
What is the difference between clean and dirty price?
The clean price is the quoted price without accrued interest, so it does not jump on coupon dates. The dirty (or full, or invoice) price is clean price plus accrued interest, and it is what you actually pay.
Which convention does my bond use?
US Treasuries: actual/actual. US corporates, agencies and municipals: 30/360. Eurobonds and many European corporates: 30E/360 or actual/actual. Most government bonds outside the US: actual/actual. Money-market instruments: actual/360 or actual/365. The prospectus or your broker’s trade details state it.
What does the yield option do?
With the maturity date, the calculator counts the coupons left and discounts them and the final repayment at your yield, with the first payment a part period away, to get the dirty price. Subtracting accrued interest gives the clean price. It follows the same convention as the PRICE function in spreadsheets, so the results match.
Can accrued interest be negative?
Yes, on bonds that trade ex-coupon. Some UK gilts and Australian bonds go ex-dividend a few days before the coupon date, so a buyer in that window does not get the next coupon and the seller pays them interest instead. This calculator does not model ex-coupon periods.
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Educational estimate, not financial or tax advice. Rules and thresholds change — confirm current figures with the IRS/HMRC or a qualified adviser before acting.