White Mountains Insurance Group will buy back 13.5 per cent of its own shares after its tender offer to shareholders was oversubscribed.

The Bermudian company said, in total, it will spend $513.4 million buying back shares at the tender offer’s final purchase price of $875 per share.

Under the “modified Dutch auction”, White Mountains was planning to repurchase up to 500,000 shares. Nearly 720,000 shares were tendered.

The company opted to purchase 86,733 shares in addition to half million planned, pursuant to the terms of the offer.

The company expects to have approximately 3.75 million common shares outstanding after it pays for the accepted shares.

On the Nasdaq Stock Exchange in lunchtime trading today, White Mountains shares were $2.92, or 0.35 per cent, higher, at $846.97, giving the company a market capitalisation of $3.67 billion.