How we calculate

We use clean prices per £100 nominal (the price before accrued interest), refreshed every 15 minutes during market hours. For conventional gilts they sit at the market mid-price: compared with official closing prices, the median difference is under 1p per £100.

We cover every conventional gilt, index-linked gilts issued since 2005, and, in the calculator only, sterling corporate bonds.

A purchase settles the next UK business day (T+1) for gilts, and two business days later (T+2) for corporate bonds. Business days exclude weekends and England and Wales bank holidays. All calculations are made as at the settlement date.

Gilts pay half their annual coupon twice a year: on the maturity date and six months either side of it. A gilt maturing on 22 October pays on 22 April and 22 October. Corporate bonds pay once or twice a year, as stated for each bond.

Buying between coupon dates means paying the seller the interest they've earned since the last coupon. We work it out on an actual/actual basis:

Gilts go ex-dividend seven business days before each coupon. If you settle after that date you don't receive the next coupon, so the seller pays you instead and accrued interest is negative:

The price you actually pay, the dirty price, is the clean price plus accrued interest.

Yield to maturity is the single yearly rate at which everything you'll receive (each remaining coupon and the £100 at maturity) is worth exactly the dirty price today. We use the Debt Management Office's formula, discounting each payment from its actual date:

There's no closed-form answer, so we solve for y numerically.

Coupons are taxed as income. Gains on gilts, including the rise from the price you pay to the £100 you get back, are free of Capital Gains Tax. So the after-tax yield uses the same formula with each coupon reduced by your income tax rate and the repayment left untaxed:

That's why a low-coupon gilt bought well below £100 keeps most of its yield after tax, while a high-coupon gilt loses much more.

The running yield is the income return only:

For an amount you enter, we buy whole units of £100 nominal at the dirty price and hold them to maturity:

The annualised return assumes coupons are kept as cash, so for long-dated gilts it's lower than the yield to maturity, which assumes they're reinvested at the same rate.

Index-linked gilts are quoted in real terms: the price, coupons and accrued interest are per £100 before the inflation uplift. Running those real cash flows through the same yield formula gives the real yield, the return on top of RPI inflation, which is the figure the market quotes.

To compare with conventional gilts we also show an estimate including inflation, at the rate you choose (3% a year by default):

After tax, only the inflation-uplifted coupons are taxed; the uplift on the £100 repayment is free of Capital Gains Tax. Pound figures are per £100 of real value: the index ratio that turns the quoted price into the cash price scales every later payment by the same amount, so it doesn't change the return.

The two index-linked gilts issued before 2005 (4⅛% 2030 and 2% 2035) use older indexation rules and are quoted with inflation already added, so we don't include them.

Sterling corporate bonds use the same yield method, with each bond's own coupon frequency, settlement two business days after the trade, and no ex-dividend period. Most are qualifying corporate bonds, so gains are free of Capital Gains Tax and only coupons are taxed.

• Bonds without a maturity date (perpetuals) aren't shown.
• Bonds within about three months of maturity aren't shown: their quoted prices are often stale, and a small gap to £100 turns into a misleading annual yield.
• Figures assume the bond is repaid in full at maturity. Some bonds can be repaid early or in instalments, which can reduce your return.
• Unlike gilts, corporate bonds carry the risk that the company can't pay.

We test the calculations against the Debt Management Office's published reference prices for every trading day of 2016 and 2017. These tests run automatically whenever the code changes.

• Conventional gilts: 15,994 of 16,612 gilt-days match accrued interest to six decimal places and yield to within 0.000002 percentage points. The rest are newly issued gilts in an irregular first coupon period, within 0.0004 percentage points.
• Index-linked gilts: 9,105 of 9,124 gilt-days match the real yield to within 0.000002 percentage points; the other 19 (one gilt's irregular first coupon) are within 0.002.
• Current gilts: against Tradeweb FTSE official closing prices for September 2026, accrued interest matches for 69 of 71 conventional gilts and yields match for every gilt with a year or more to run. Index-linked real yields match on every day checked.

• Newly issued gilts can have a longer or shorter first coupon period. Until that first coupon, accrued interest can differ slightly from the official figure; the yield is affected by less than 0.001 percentage points.
• For gilts with under a year to run we use the Debt Management Office's compound formula. Some data providers quote a simple (money-market) yield instead, which can differ by up to about 0.05 percentage points.
• The Accrued Income Scheme, which can move part of one coupon between tax years for holdings over £5,000 nominal, isn't modelled.
• Figures use mid-market prices and exclude dealing costs and the spread between buying and selling prices. Prices may be delayed.
• Index-linked figures including inflation depend on your inflation assumption; the real yield doesn't.

Everything here is information, not financial advice. If you sell before a bond is repaid, you may get back less than you paid.