What is accrued interest on a bond?

Accrued interest is the interest that has accumulated on a bond since its last coupon payment date. When a bond is traded between coupon dates, the buyer compensates the seller for this earned-but-unpaid interest by paying the dirty price (clean price + accrued interest).

What is the difference between clean price and dirty price?

The clean price is the market quote expressed as a percentage of par or dollar amount excluding accrued interest. The dirty price (or settlement/invoice price) is the total cash paid by the buyer to the seller, equal to the clean dollar price plus accrued interest.

How does Actual/Actual ICMA work for US Treasuries?

US Treasury notes and bonds use the Actual/Actual ICMA convention for regular coupon periods (31 CFR Part 356). It calculates the exact number of calendar days from the last coupon date to settlement divided by the exact number of calendar days in the full coupon period between the last and next coupon dates.

How does the US 30/360 Bond Basis convention work?

The US 30/360 convention assumes 30 days per month and 360 days per year. It applies specific end-of-month adjustments: if the last coupon date falls on the 31st or the last day of February, it is adjusted to day 30, and similar rules apply to settlement to maintain a 30-day month uniform basis.

Which convention is used for corporate and municipal bonds?

In the United States, municipal bonds (per MSRB rules) and corporate bonds standardly trade on a 30/360 day count basis. Eurobonds and commercial paper commonly use Actual/360 or Actual/365 Fixed.

Is the settlement date the same as the trade date?

No. The settlement date is when the transaction actually settles (cash and bonds change hands), typically T+1 or T+2 after the trade date. Accrued interest is calculated to the settlement date, not the trade date.

How do I calculate accrued interest on a bond step by step?

Find the coupon per period (face × rate ÷ frequency), count the days from the last coupon date to settlement, divide by the days in the coupon period, and multiply. For a $1,000 bond paying 5% semiannually ($25 a period), settling 85 days into a 180-day 30/360 period, accrued interest is $25 × 85 ÷ 180 = $11.81. Under Actual/Actual the same dates give 85 ÷ 181 × $25 = $11.74.

How do I find the last and next coupon dates?

Coupons are paid on the maturity date's day of the month, every 12 ÷ frequency months. A bond maturing on July 15 that pays semiannually pays on January 15 and July 15. Count back from maturity until you reach a date on or before settlement; that is the last coupon, and the one after it is the next. If maturity is the last day of a month, every coupon falls on a month-end.

How do I check this in Excel?

Use ACCRINT(issue, first_interest, settlement, rate, par, frequency, basis) with the last coupon date as issue and the next coupon date as first_interest. Basis 0 is 30/360 US, 1 is Actual/Actual, 2 is Actual/360 and 3 is Actual/365. The calculator shows the formula filled in with your inputs.

Is this financial advice?

No. This is an educational calculator for regular coupon periods. Trade confirmations can differ because of odd first or last coupons, ex-coupon periods, holidays, fees and the bond's own terms, so rely on your broker's confirmation for actual amounts.

What happens if settlement occurs on a coupon payment date?

If a bond settles on the coupon payment date, the accrued interest is $0.00. The seller receives the full coupon payment directly from the issuer, and the dirty price equals the clean price.

Accrued Interest Bond Calculator

Enter face value, coupon, maturity and settlement date to get accrued interest, the dirty price you pay, and a side-by-side of all four day-count conventions.

Accrued interest = face value × annual coupon rate ÷ payments per year × (days accrued ÷ days in the coupon period).

Bond Parameters

Face Value ($)

Annual Coupon Rate (%)

Quoted Price (% of Par)

Bonds are usually quoted clean (without accrued interest).

Payment Frequency

Settlement Date

Maturity Date (fills the coupon dates)

Coupons fall on the maturity day every 12 ÷ frequency months.

Last Coupon Payment Date

Next Coupon Payment Date

Day Count Convention

Fill in the parameters and click
Calculate Accrued Interest

Accrued Days

—

days since last coupon

Period Length

—

days in coupon period

Clean Price ($)

$0.00

Quote: 100.00% of par

Dirty / Settlement Price

$0.00

Invoice: 100.00% of par

Accrued Interest

$0.00 per $1,000 face value

Day count convention —

Coupon per period —

Accrued clean dollar —

Total dirty settlement —

Accrual fraction —

Convention Comparison

Actual/Actual ICMA uses exact days in the regular coupon period. Corporate & municipal bonds typically use US 30/360.
Convention	Days	Period	Accrued Int.	Dirty Price

Regular coupon periods only. Check the security documents for odd first or final coupons, ex-coupon rules, fees, taxes, and the contractual day-count convention.

Check in Excel or Google Sheets

—

ACCRINT with the last coupon as issue and the next coupon as first_interest. Basis 0 = 30/360 US, 1 = Actual/Actual, 2 = Actual/360, 3 = Actual/365.

Day-Count Conventions at a Glance

Convention	Accrual fraction	Typically used for	Excel basis
30/360 US (Bond Basis)	30-day months: D1=31→30; D2=31→30 if D1 ≥ 30; Feb month-end rules. Days ÷ 360 × frequency	US corporate, agency and municipal bonds	0
Actual/Actual ICMA	Actual days ÷ actual days in the coupon period	US Treasury notes and bonds, most government bonds	1
Actual/360	Actual days ÷ 360 × frequency	Money markets, commercial paper, many floating-rate notes	2
Actual/365 Fixed	Actual days ÷ 365 × frequency	Sterling and some Commonwealth money markets	3

Educational tool, not financial advice. Your broker's trade confirmation is the authoritative amount; odd coupons, ex-coupon periods and holiday adjustments are not modeled.

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Quick answer

Accrued interest = face value × annual coupon rate ÷ payments per year × (days accrued ÷ days in the coupon period). Count days from the last coupon date to settlement using the bond's convention: 30/360 for US corporates and munis, Actual/Actual for Treasuries. Dirty (invoice) price = clean price + accrued interest.

Examples

$1,000, 5% semiannual, Jan 15 → settle Apr 10, 2026	Days	Accrued
30/360 US	85 / 180	$11.81
Actual/Actual ICMA	85 / 181	$11.74
Actual/360	85 / 360	$11.81
Actual/365 Fixed	85 / 365	$11.64

Enter the coupon, maturity and settlement date to get accrued interest and the dirty price under every convention.

Summary

This calculator computes the interest a bond has earned since its last coupon date, which the buyer pays the seller at settlement. Enter the maturity date and it finds the last and next coupon dates for you, or type them in directly. It shows the accrued interest, the clean and dirty (invoice) price, and the same trade under 30/360 US, Actual/Actual ICMA, Actual/360 and Actual/365 Fixed. An Excel ACCRINT formula lets you check the result. Educational estimate for regular coupon periods, not financial advice.

How it works

Enter the bond face value (par value), annual coupon rate and the quoted price (% of par), and say whether the quote is clean or dirty.
Select the payment frequency: annual, semi-annual, quarterly or monthly.
Enter the settlement date and the maturity date, then click "Find coupon dates" — or enter the last and next coupon dates yourself.
Choose the day count convention: Actual/Actual ICMA (Treasuries), 30/360 US (corporates and munis), Actual/360 or Actual/365 Fixed.
Read the accrued interest, clean and dirty price, the cross-convention comparison and the matching Excel ACCRINT formula.

Use cases

Price bonds being bought or sold between coupon payment dates.
Reconcile bond settlement amounts on trade confirmation.
Verify accrued interest figures reported by brokers or custodians.
Compare accrued interest under different day count conventions.
Calculate clean price from dirty price (or vice versa).
Support fixed income portfolio accounting and valuation.
Teach bond math and day count conventions in finance courses.
Audit coupon accrual entries in accounting systems.

Frequently Asked Questions

Last updated: 2026-10-10 · Reviewed by Nham Vu