Bond Calculator

Fill in the four inputs below and the tool will compute the bond’s outstanding value. It works for bonds that are issued or traded on their coupon date.

Bond pricing calculator

This calculator evaluates the price of bonds bought or sold away from the coupon date, delivering the dirty price, clean price, accrued interest and the number of days since the previous coupon.

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The first tool above calculates several attributes of a fixed‑rate coupon bond when it is issued or exchanged on its coupon date. The second tool determines the price and accrued interest for fixed‑rate bonds traded off‑coupon, employing standard day‑count conventions. Keep in mind these utilities are tailored for fixed‑rate coupon bonds, which make up most bond issues. They do not incorporate additional influences such as credit risk, market supply‑demand dynamics, or other pricing factors.

What is a bond?

A bond is a debt security through which an investor lends money to an issuer—usually a corporation or a government. It enables the issuer to obtain financing, outlining the loan conditions and the schedule of payments to the bondholder.

There are many bond categories designed to meet the differing objectives of investors and issuers, each with distinct features, risk profiles, and advantages. The most prevalent groups are sovereign (government) bonds, municipal bonds, corporate bonds, and high‑yield or junk bonds.

Compared with equities, bonds generally present less risk, which appeals to investors seeking steady cash flow and capital protection. Still, bond risk and reward differ greatly based on the issuer’s credit strength and the instrument’s term. For instance, top‑tier sovereign bonds like U.S. Treasuries are deemed very safe, whereas high‑yield corporate (junk) bonds entail considerably higher risk.

Bond structure

A bond’s structure comprises several elements that define its behavior as a financial instrument. Below is an overview of the principal components of a bond:

2. Face value—Also called par value, this is the sum the issuer promises to return to the holder when the bond matures, and it forms the reference point for computing coupon interest.
4. Maturity date—The date on which the principal must be repaid to the investor. Bonds may be short‑, medium‑, or long‑dated, ranging from under a year to more than three decades. The phrase “time to maturity” denotes the remaining interval until that date.
6. Coupon rate—This is the percentage of the face value that the issuer agrees to pay as interest, usually on an annual or semi‑annual schedule. Rates may be fixed, floating, or zero (in zero‑coupon bonds). The tools above only support bonds with a fixed coupon rate.
8. Coupon payment frequency—Indicates the interval at which the issuer disburses coupon payments to investors. Typical schedules are yearly, semi‑annual, quarterly, or monthly.
10. Yield—The yield shows the expected return for an investor who holds the bond to maturity. Expressed as an annual rate, it depends on the purchase price, face value, coupon rate and time left to maturity. Various yield measures exist; the calculators above use the current yield, which compares the annual coupon amount to the bond’s market price, not its par value. Current yield equals annual coupon divided by market price and varies as the price moves.
12. Price—A bond’s market price is the amount for which it can be bought or sold. It reflects the discounted value of all future coupon payments plus the principal repayment, adjusted for credit risk, time to maturity and prevailing interest rates.

Beyond these core components, features such as the issuer, call and put options, credit rating, covenants, and marketability also play important roles in a bond's valuation.

How to calculate the bond price?

To determine a bond’s price you discount each future cash flow—both coupon payments and the principal repayment—back to the present using the required yield or discount rate. Summing these present values yields the bond’s price. The fundamental pricing formula is shown below:

where:

C = the coupon payment per period,
N = number of periods until maturity,
r = the discount rate or yield per period,
F = the face value of the bond.

Clean price and dirty price

Bond valuation often assumes trading on the coupon date, yet most transactions occur between coupon dates. In those cases the market quotes either a ‘clean price’ or a ‘dirty price’. Understanding both concepts is essential for accurate bond pricing.

Accrued interest

Accrued interest represents the interest that has built up since the last coupon payment but has not yet been received by the bondholder. It can be calculated with the following formula:

Clean price

The clean price is the bond’s value excluding any accrued interest since the previous coupon. Market quotations typically use the clean price, providing a consistent basis for comparing bonds regardless of differing accrual periods.

Dirty price (invoice price)

The dirty price, also called the invoice price, adds accrued interest to the clean price. It reflects the total amount the buyer pays the seller, accounting for interest earned up to the settlement date, and therefore gives a complete valuation of the bond between coupon dates.

Based on the definitions above, the relationship between clean and dirty prices can be summarized as:

dirty price = clean price + accrued interest

This formula highlights that the dirty price, which is the total price paid by the buyer, includes both the clean price of the bond (its market value excluding accrued interest) and the accrued interest earned on the bond from the last coupon payment date up to the purchase date.

Day-count conventions

Accrued interest calculations rely on day‑count conventions, which define how the number of days since the last coupon and the total days in a year are counted. The most common conventions in the bond market are listed below:

• 30/360 (bond basis): This convention assumes each month consists of 30 days and a year of 360 days. By fixing month and year lengths, it makes manual accrued‑interest calculations straightforward. It is commonly applied to corporate, agency and municipal bonds in the U.S.
• Actual/360 (A/360): Under this method the exact number of days in the accrual period is counted, while the year is treated as 360 days. It is the typical choice for money‑market instruments such as commercial paper and short‑term bank CDs.
• Actual/365 (A/365): This method uses the actual number of days in the accrual period but assumes a fixed year length of 365 days (although leap years, which have 366 days, are usually not accounted for). It is commonly used for some government bonds outside the United States and in some interest rate swaps.
• Actual/Actual (A/A): Primarily used for government securities, including U.S. Treasuries, this convention counts the real number of days in both the accrual period and the calendar year, delivering the most accurate result.

Various bonds adopt different day‑count conventions. The selected convention influences how accrued interest is computed and consequently the quoted price of a bond traded between coupon dates. Our second calculator lets you pick the convention you need. In practice the variation in accrued interest between conventions is tiny; only in extreme scenarios can it amount to roughly six days of interest.

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