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Bonds · Lesson 09 of 11

Convertible Bonds

6 min read  ·  Advanced

A convertible bond is exactly what it sounds like: a bond that can convert into shares of the issuing company. It's a hybrid instrument — part debt, part equity option — and it behaves differently from either. Companies issue them; sophisticated investors collect them; and they're fascinating to understand because they sit right at the intersection of equity and debt markets.

The basic mechanics

A convertible bond pays a coupon like any bond and repays principal at maturity — but it also includes the option to convert into a set number of company shares at a predetermined price (the conversion price). The holder decides whether to convert or redeem for cash at maturity.

Convertible bond example
Face value£1,000
Coupon2% (lower than straight bond)
Conversion price£50 per share
Conversion ratio20 shares per bond

If shares rise to £80: convert → receive 20 shares worth £1,600. If shares stay at £30: don't convert → receive £1,000 principal back. The bond gives you downside protection with upside participation.

Why companies issue convertibles

Companies issue convertibles to borrow cheaply. Because they include an equity option, investors accept a lower coupon than they'd demand for a straight bond. For a company whose shares are volatile or whose credit rating isn't stellar, convertibles are often the cheapest way to raise debt. Tech companies and growth businesses issue them frequently.

The downside for existing shareholders: if the bond converts, new shares are issued, diluting existing ownership. It's borrowing now at the cost of potential dilution later.

The conversion premium

The conversion premium is the percentage by which the conversion price exceeds the current share price. A 30% conversion premium means the share price needs to rise 30% before conversion becomes attractive. Convertibles with low premiums behave more like stocks (share price close to conversion level). Those with high premiums behave more like bonds (share price far from conversion, so the equity option is worth little).

The busted convertible

A busted convertible is one where the share price has fallen so far below the conversion price that conversion is essentially worthless. The instrument now trades purely as a bond, based on credit quality and yield. Distressed investors sometimes buy busted convertibles at a deep discount, hoping either that the share price recovers or that the company's credit improves — either outcome produces a profit.

Why convertibles matter for equity investors: when a company you follow issues a convertible bond, pay attention to the terms. The conversion price signals where management thinks the share price is going — they price it at a premium to current levels but not so high as to be useless. It's a subtle form of management signalling about their own valuation view.

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