Bond Yield Calculator Guide: Current Yield and Yield to Maturity

A bond's coupon rate is not its return. A bond that pays 5 percent on its face value can return more or less than 5 percent to its buyer, depending on the price paid for it. Buy below face value and the return rises, because the buyer also gains when the bond is repaid at full face value. Buy above face value and the return falls, because part of that repayment is given back. Yield is the number that captures this, and there are two yields every bond buyer should understand.

The Bond Yield Calculator takes face value, annual coupon payment, current price, and years to maturity, and returns current yield and an approximate yield to maturity. This guide explains both, works through an example, and shows what the approximation leaves out. The figures are educational estimates, not financial advice, and not a recommendation to buy or sell any bond.

Current yield: income over price

Current yield is the simplest yield: annual coupon divided by current price. It answers the question, "how much income do I get each year relative to what I paid?" It ignores any gain or loss when the bond matures, which makes it easy to compute but incomplete as a return measure, especially for bonds bought far from face value or with many years left.

A bond with a face value of 1,000 paying a 50 annual coupon has a coupon rate of 5 percent. If it can be bought for 950, the current yield is 50 divided by 950, which equals about 5.26 percent. The income is the same 50, but it is earned on a smaller investment, so the yield is higher than the coupon rate. If the same bond cost 1,050, the current yield would be 50 divided by 1,050, or about 4.76 percent, lower than the coupon rate for the mirror-image reason.

Yield to maturity: the fuller picture

Yield to maturity, or YTM, is the single annual rate that equates the bond's price with all its future payments: every coupon plus the face value at maturity. It accounts for both the income and the capital gain or loss at maturity, spread over the remaining years. That makes it the better comparison figure between bonds, but it is harder to calculate exactly, because solving for it requires trial and error or a financial calculator.

The common approximation spreads the capital gain or loss evenly over the remaining years and divides by the average of face value and price. The formula is: annual coupon plus the yearly share of the price difference, all divided by the average of face value and price. It is close to the true YTM for most ordinary bonds, and it is what this calculator returns, labelled as approximate for exactly that reason.

Worked example: 1,000 face value, 50 coupon, 950 price, 10 years

Take a bond with a face value of 1,000, an annual coupon of 50, a price of 950, and 10 years to maturity. Current yield is 50 divided by 950, which equals 0.0526, or about 5.26 percent. For approximate YTM, first find the yearly share of the price gain: face value minus price is 1,000 minus 950, which equals 50, and spread over 10 years that is 5 per year. Add the coupon: 50 plus 5 equals 55. Next, average face value and price: 1,000 plus 950 equals 1,950, divided by 2 equals 975. Finally, 55 divided by 975 equals 0.0564, or about 5.64 percent.

So the bond's current yield is about 5.26 percent and its approximate yield to maturity is about 5.64 percent. The YTM is higher because the buyer gains 50 at maturity on top of the coupons, and that gain adds roughly 0.38 percentage points per year. If the bond had been bought above face value, the YTM would be lower than the current yield by the mirror-image logic.

What the approximation leaves out

The approximation assumes the capital gain is spread evenly, which is close but not exact, because money received sooner is worth more than money received later. The true YTM for the example bond is slightly different from 5.64 percent, though close enough for comparison purposes. The approximation also assumes coupons are reinvested at the YTM itself, which is the standard YTM assumption and rarely holds exactly in practice: real reinvestment rates vary with market conditions.

The calculator also assumes the bond will be held to maturity and that the issuer will pay in full. Credit risk, the chance the issuer defaults or restructures, is not in the formula, and neither are taxes, trading costs, or inflation. A high yield often signals high risk rather than a bargain, and a yield comparison that ignores credit quality is misleading.

Common mistakes

The most common mistake is comparing coupon rates instead of yields. Two bonds with the same coupon can have very different yields if their prices differ, and the cheaper bond is not automatically better if its issuer is riskier or its maturity is much longer. Compare YTM alongside maturity and credit quality, not alone.

The second mistake is forgetting that price and yield move in opposite directions. When market interest rates rise, existing bond prices fall, and their yields rise; when rates fall, prices rise and yields fall. A bond whose price has fallen has not necessarily become a worse investment; for a new buyer, its yield has improved, though its previous owner has lost value.

The third mistake is treating YTM as a guaranteed return. It is a promised return if the bond is held to maturity, coupons are reinvested at the same rate, and the issuer pays in full. Any of those conditions can fail, and the realised return can differ substantially.

A short practical routine

When comparing bonds, note face value, coupon, price, and years to maturity, and run the calculator for current yield and approximate YTM. Compare YTMs only between bonds of similar maturity and credit quality, and check the issuer's standing separately. If a yield looks far above similar bonds, ask what risk the market is pricing in before treating it as an opportunity.

For related return maths, the Compound Interest Calculator shows how reinvested income compounds, the Simple Interest Calculator contrasts the non-compounding case, and the ROI Calculator frames returns for other investments. For more on getting percentages right, see How to Calculate Marks Percentage Correctly Every Time.

The takeaway

Current yield is income over price; yield to maturity adds the price gain or loss at maturity. Use YTM for comparisons, remember it is approximate and assumes full payment and reinvestment, and never judge a bond by yield alone without checking maturity and credit risk.