It's the Holy Grail of value investing: to 'buy a dollar for 50 cents' and it's not as hard as you think.

To find undervalued companies you can start with identifying businesses which sell for less than their book value or net tangible assets (NTA). A price-to-book ratio of less than 1 means a company sells for less than the value of its net assets and is worthy of a closer look.

To get you started, here are five potential hidden stocks which may have been missed by investors.

EVOLUTION FPO (ASX: EVN)

Price to book value: 0.44

Shares in gold miner Evolution Mining have been languishing after a 24% slide in the last six months. But the company screams out as a potential value play at a share price of $0.69 per share and with declared net tangible assets of $1.56 per share as at 30 June 2014.

The company is profitable and pays a dividend, while production outlook for FY15 is in-line with 2014 at up to 440,000 ounces of gold. Evolution's all-in sustaining cost forecast is at between $1,050 and $1,130 per oz.

Merchant House International Limited (ASX: MHI)

Price to book value: 0.55

Merchant House International is a small textile and clothing manufacturer based in China. The company has plans to start production in the U.S., but currently has net tangible assets worth almost twice its $21 million market capitalisation.

Not only that, but the company's cash and cash equivalents make up $15 million (71%) of this market capitalisation! This is a classic "buy a dollar for 50 cents" play. Investors should note however that the company is registered in the tax haven of Bermuda.

Beach Energy Ltd (ASX: BPT)

Price to book value: 0.92

The falling price of oil has seen 25% wiped off the value of shares in energy producer Beach Energy Ltd in the last three months and the company now trades at a price-to-book value of 0.92.

In Beach Energy's 2014 annual report the company declared net assets of $1.8 billion, yet has a market cap of just $1.67 billion. This could make the company one of the great bargains of the oil industry at the moment.

Cooper Energy Ltd. (ASX: COE)

Price to book value: 0.78

Similarly, shares in Cooper Energy Ltd have been smashed 27% in the last three months, pushing the company's market capitalisation to $131.7 million: below the company's most recently declared net (tangible) assets of $167.8 million.

Contango MicroCap Limited (ASX: CTN)

Price to investment book value: 0.91

Small-cap investment company Contango MicroCap Limited has an enviable reputation for growing returns, while paying a sizeable dividend of over 8%. The company provides monthly updates on the net tangible value of its investments, the most recent of which (September 2014) was $1.12 per share.

Shares in Contango currently sell for $1.02, leaving a sizeable safety margin. This disparity perhaps reflects uncertainty around the price of the underlying companies held, or an allowance for the cost of liquidating the positions. Regardless, the company remains a great way to gain exposure to a number of small and growing companies at an attractive price.

The post 5 bargain companies trading below book value today appeared first on The Motley Fool Australia.