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Definition in Loans, Bonds, Investments, Transactions

What Is Principal?

Principal is most commonly used to refer to the original sum of money borrowed in a loan or put into an investment. It can also refer to the face value of a bond, the owner of a private company, or the chief participant in a transaction.

Key Takeaways

  • The term “principal” has several meanings in the financial and business world.
  • In the context of borrowing, principal is the initial size of a loan or a bond (the amount that must be repay).
  • In the context of investing, principal is the original sum committed to the purchase of assets (independent of any earnings or interest)
  • In business, principals are those who own a majority stake in a company and/or play a significant role in running it.
  • In contracts and contractural ventures, principals are the chief parties involved in the transaction who have rights, duties, and obligations regarding it.

Understanding Principal

In the context of borrowing, principal is the initial size of a loan—it can also be the amount still owed on a loan. If you take out a $50,000 mortgage, for example, the principal is $50,000. If you pay off $30,000, the principal balance now consists of the remaining $20,000.

The amount of interest you pay on a loan is determined by the principal. When you make monthly payments on a loan, the amount of your payment goes first to cover accrued interest charges; only then is the remainder applied to your principal. Paying down the principal of a loan is the only way to reduce the amount of interest that accrues each month.

A zero-coupon mortgage is a type of financing in which the borrower’s regular payments cover only the interest charged on the loan, as opposed to both interest and principal. As a result, the borrower does not make any progress in reducing the loan’s principal balance—or on building equity in the mortgaged property.

Special Considerations

Inflation does not affect the nominal value of the principal of a loan, bond, or other financial instruments. However, inflation does erode the real value of the principal.

Suppose the U.S. government issues $10 million worth of 10-year U.S. Treasury bonds. Each treasury has a face value, or principal, of $10,000. If the average annual rate of inflation over the next 10 years is 4%, then the real value of those bonds at maturity is only $6,755,641.69.

Yes, the principal balance remains $10,000, and that’s the nominal sum bondholders receive. However, the value of that $10,000 (that is, what it can buy) has declined to, effectively, $6,755.64. In other words, the principal has only 67% of its original purchasing power.

Bondholders can still recoup their original costs if the value of the interest income the bond has generated is greater than the lost principal value. They can track the amount of return, or yieldthey’re getting on a bond.

There’s the bond’s nominal yieldwhich is the interest paid divided by the principal of the bond, and its current yieldwhich equals the annual interest generated by the bond divided by its current market price.

Types of Principal

Beyond loan principal, there are four other key types of principal.


Principal is also the original amount of investment made in an asset, separate from any earnings or interest accrued. For example, assume you deposit $5,000 in an interest-bearing savings account. At the end of 10 years, your account balance will have grown to $6,500. The $5,000 you initially deposited is your principal, while the remaining $1,500 is attributed to earnings.

The Various Definitions of Principal
Different Types of Principal Definition
Loans The sum of money borrowed
Investments The amount of money put into an investment
Bonds The face value of a bond
Companies The owner of a private company, partnership, or other type of firm
Transactions The party that has the power to transact on behalf of an organization or account and takes on the attendant risk, whether it be an individual, a corporation, a partnership, a government agency, or a nonprofit organization.


In the context of debt instrumentsprincipal is the amount of money the issuer of a bond is borrowing and will repay to the bondholder in full upon the bond’s maturity. A bond’s principal is also known as its “by value” or “face value” (because, back in the days when bonds were actual physical pieces of paper, this amount was printed on the face of the bond itself).

The bond’s principal is exclusive of any couponrecurring interest payments, or accrued interest (although the issuer is obligated to pay these as well). For instance, a 10-year bond may be issued with $10,000 face value and have $50 recurring coupon payments semiannually. The principal is $10,000, independent of the $1,000 worth of coupon payments over the life of the bond.

Except when it is first issued, a bond’s principal is not necessarily the same as its market price. Depending on the state of the bond marketa bond may be purchased for more or less than its principal.

Private Companies

The owner of a private company, partnership, or other type of firm is also referred to as a “principal.” This is not necessarily the same as a CEO. A principal could be an officer, a shareholder, a board member, or even a key sales employee—basically, it’s the primary investor or the person who owns the largest share of the business.

A company may also have several principals, who all have the same equity stake in the concern. Anyone considering investing in a private venture will want to know its principals in order to assess the business’ creditworthiness and potential for growth.

Responsible Parties

The term “principal” also refers to the party who has the power to transact on behalf of an organization or account and takes on the attendant risk. A principal can be an individual, a corporation, a partnershipa government agency, or a nonprofit organization. Principals may elect to appoint agents to operate on their behalf.

The transaction a principal is involved in could be anything from a corporate acquisition to a mortgage. The term is usually defined in the transaction’s legal documents. In those documents the principal is everyone who signed the agreement and thus has rights, duties, and obligations regarding the transaction.

When a person hires a financial advisorthey are considered a principal, while the advisor is the agent. The agent follows instructions given by the principal and may act on their behalf within specified parameters. While the advisor is often bound by fiduciary duty to act in the principal’s best interests, the principal retains the risk for any action or inaction on the part of the agent. If the agent makes a bad investment, it is still the principal who loses the money.

How Do You Find the Principal Amount?

The formula for calculating the principal amount when there is simple interest is P = I / (RT), which is the interest amount divided by the interest rate times the amount of time.

How Does Compounding Grow Your Principal?

The principal amount of an investment can earn interest, but compounding is when the interest you earn is added back to the principal balance. Effectively you’re earning interest on your interest—compounding your return.

What Factors Determine the Interest Charged on Principal?

The interest you will pay on the principal balance of a loan is largely determined by your credit score and credit history. Other factors include the loan type and length of loan. For a home loan, the property location, loan amount, and down payment will also be key factors.

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