Why Companies Issue Convertible Bonds

A growth company wants to raise $300 million. A straight bond might cost it 7% a year in interest. Selling stock outright avoids interest payments but hands new investors shares at today's price — the cheapest price the stock is ever likely to be, if management believes its own growth story. A convertible bond is the compromise: bondholders lend money at a coupon well below the straight-debt rate, in exchange for the right to convert their bonds into shares later at a fixed price above today's — usually 20-40% higher.

Why the company likes it

The coupon discount is the whole point. Investors accept a lower yield because the conversion option gives them upside they wouldn't get from a plain bond — so the company effectively finances part of its debt with equity-like value instead of cash interest. For a company whose stock is volatile (which makes the embedded option more valuable to investors) but whose credit is decent, this can be much cheaper than either straight debt or straight equity alone. It also delays dilution: shares only get issued if and when the stock rises above the conversion price, not on day one.

Why the company should be careful

The discount isn't free. If the stock rallies past the conversion price, the company has sold shares at a premium to issuance-day price, but still a premium below wherever the stock eventually trades — every dollar of stock appreciation above the conversion price effectively transfers from existing shareholders to convert-holders. And if the stock never gets there, the company has simply borrowed money, due in full at maturity, with none of the upside benefit realized. Many convertibles are also callable or contain investor put dates, and issuers often buy back capped calls at issuance specifically to raise the effective conversion price and reduce dilution.

Worked example

A company's stock trades at $40. It issues a 5-year convertible with a coupon of 2% instead of the 6.5% it would pay on a straight bond, and a conversion price of $52 (a 30% premium to $40).

• Cash saved on interest: on $300 million principal, the coupon gap is $6.5\% - 2\% = 4.5\%$ per year, or $13.5 million a year in reduced interest — real cash the company keeps.
• What bondholders are owed if the stock never reaches $52: their bonds are simply repaid at par, $300 million, having collected the 2% coupon along the way. The company paid $13.5 million a year for a bet that didn't pay off for investors — but the company still saved cash versus a straight bond.
• What happens if the stock hits $65 at maturity: each $1,000 bond converts into $1{,}000 / 52 \approx 19.2$ shares, worth 19.2 \times \65 \approx $1{,}250 — bondholders do far better than getting \1,000 back, and the company has issued shares at $52 each rather than the $65 they were actually worth by then.

What this means in practice

Convertibles show up most often at growth companies with high stock volatility (which makes the option investors receive more valuable, letting the company cut the coupon further) and at companies wanting to avoid an immediate, visible equity issuance. They also attract a specific buyer base — convertible arbitrage funds that buy the bond and short the stock to isolate the option's value — which is why convertible issuance and hedge-fund short interest often move together.