Accrued Interest Calculator for Bonds

An accrued interest calculator for bonds estimates the interest earned since the bond’s last coupon payment. Enter the bond’s annual coupon rate, face value, and days elapsed and in the coupon period; the calculator returns accrued interest, using a simple day-count fraction.

Formula

This calculator uses a proportional coupon-accrual formula:

Accrued interest = face value × (annual coupon rate ÷ 100) × (days elapsed ÷ days in coupon period)

• Face value is the principal amount used to calculate the bond’s coupon, in dollars.
• Annual coupon rate is the stated yearly rate as a percentage.
• Days elapsed is the number of days from the previous coupon date to the settlement or calculation date.
• Days in coupon period is the total number of days from one scheduled coupon date to the next.
• Accrued interest is the estimated interest accumulated during the elapsed part of the period, in dollars.

The calculator’s second result is annual coupon interest: face value multiplied by the annual coupon rate as a decimal. The main result is an estimate based on the day fraction you enter; it does not determine coupon dates or select a market convention for you.

Worked Example

Using the calculator’s default inputs: face value $1,000, annual coupon rate 5%, 90 elapsed days, and a 180-day coupon period.

1. Convert the rate to decimal form: 5 ÷ 100 = 0.05.
2. Calculate annual coupon interest: $1,000 × 0.05 = $50.00.
3. Find the elapsed portion of the period: 90 ÷ 180 = 0.5.
4. Multiply the annual coupon interest by that fraction: $50.00 × 0.5 = $25.00 accrued interest.

The calculator’s second output is $50.00 annual coupon interest. The headline result, rounded to cents, is $25.00.

Assumptions

• The coupon rate and face value remain constant during the period.
• Interest accrues in proportion to the entered elapsed-days fraction; the calculator does not infer payment timing or dates.
• This is a simple day-count calculation, not monthly compounding or a yield calculation.
• Bond price, yield, taxes, transaction charges, and any accrued-interest convention used by a market or contract are not included.
• Enter elapsed days no greater than the coupon-period days. The input limits prevent values above 365 or 366, but the calculator does not check whether elapsed days exceed your specific period.

What Accrued Interest Means for a Bond

A coupon bond promises periodic interest payments, commonly called coupons. Interest generally accumulates between scheduled coupon dates even though the investor receives the cash only on a payment date. If a bond is sold between coupon dates, accrued interest can matter in the settlement amount: in many standard bond trades, the buyer compensates the seller for interest earned during the seller’s holding period, and the buyer later receives the full coupon. The exact settlement treatment depends on the bond’s terms and applicable market convention.

Accrued interest is not the same as the bond’s market price, yield, or total return. It is the portion of coupon interest attributed to a slice of time. The bond’s quoted price may be shown without accrued interest (often called a clean price), while the amount paid at settlement may include accrued interest (often called a dirty or full price). Do not assume this calculator gives the complete amount payable for a trade.

Choosing the Day Count and Dates

The key input is not merely the calendar-day count; it is the day-count convention required for the specific bond or calculation. Common conventions include Actual/Actual, Actual/360, Actual/365, and 30/360. They differ in how they count days and define the denominator. Some also handle coupon schedules, leap years, and irregular first or final periods in specific ways.

• Identify the prior and next coupon dates from the bond’s terms.
• Use the settlement date, rather than the order date, if calculating interest for a settlement amount.
• Check the bond documentation or a reliable transaction statement for its day-count convention.
• Enter the elapsed-day numerator and period denominator that convention requires. Do not automatically substitute 365 or 360.

This calculator lets you supply the fraction directly, which makes it useful for a quick estimate but means it cannot verify dates, business-day adjustments, or convention-specific rules. For a precise trade figure, use the convention and dates applied to that bond.

Common Errors and Limits

• Entering 5 instead of 0.05 in the formula: the calculator expects the rate as a percentage, so enter 5 for 5%.
• Using the wrong period denominator: 90 elapsed days over a 180-day period is not interchangeable with 90 over 365.
• Confusing coupon rate with yield: the coupon rate determines scheduled coupon interest; yield reflects price and cash flows and is not an input here.
• Using the wrong principal: coupon calculations generally use the bond’s stated face value, not necessarily the amount paid to buy it.
• Assuming every bond pays twice a year: coupon frequency and period length vary. Use the actual schedule.

The calculation is linear: doubling face value or the elapsed fraction doubles the result, if all other inputs stay fixed. It does not model floating-rate resets, inflation adjustments, amortizing principal, zero-coupon bonds, irregular coupon periods, or a bond’s accrued-interest rules unless those details are reflected in the inputs and a suitable method. Its broad input limits are safeguards, not validation of a real bond schedule.

Frequently Asked Questions

How do I calculate accrued interest on a bond?
Multiply face value by the annual coupon rate expressed as a decimal, then multiply by the fraction of the coupon period that has elapsed. Use the bond’s required day-count convention for that fraction.

Who receives accrued interest when a bond is sold?
In many standard transactions, the buyer pays the seller accrued interest at settlement, then receives the next scheduled coupon. The actual treatment should be confirmed from the bond’s terms and trade details.

Is accrued interest included in a bond’s quoted price?
Not always. A clean quote generally excludes accrued interest; a dirty or full price includes it. Confirm which figure a quote or statement displays before comparing it with a settlement amount.

Can I use this calculator for a zero-coupon bond?
This coupon-based formula is not appropriate for a zero-coupon bond because it has no regular coupon payment. Its value changes through pricing and maturity mechanics rather than periodic coupon accrual.

Why does my broker’s accrued-interest amount differ?
Possible reasons include a different settlement date, coupon schedule, day-count convention, face amount, or rounding method. Compare those inputs and the bond’s documentation; this calculator does not resolve convention-specific differences.

This is estimate arithmetic for education, not financial advice; the bond’s terms and transaction disclosure provide the applicable figures.

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in face | Bond face value | $ | 1000 | 0.01 | 100000000
in coupon | Annual coupon rate | % | 5 | 0.01 | 100
in elapsed | Days since last coupon | days | 90 | 0 | 365
in period | Days in coupon period | days | 180 | 1 | 366
out ai | Accrued interest | $ | face * (coupon / 100) * elapsed / period | 2
out annual | Annual coupon interest | $ | face * coupon / 100 | 2