The world's biggest miner has posted an 83 per cent jump in first-half net profit to $US8.1 billion (just under $9 billion).

BHP Billiton says its revenues rose 5.9 per cent to $US33.95 billion ($37.6 billion) for the half-year to December 31, 2013.

However, when the effect of some one-off factors are excluded, BHP's underlying profit rose 31 per cent to $US7.8 billion ($8.6 billion).

The company's chief executive Andrew Mackenzie says the improved result has largely been driven by significant cost savings.

"The commitment we made 18 months ago to deliver more tonnes and more barrels from our existing infrastructure at a lower unit cost is delivering tangible results," he observed in the report.

"Annualised productivity led volume and cost efficiencies totalling $US4.9 billion are now embedded and this is expected to increase to $US5.5 billion by the end of the 2014 financial year."

Olympic Dam, which employs several thousand people in South Australia, is one focus of potential cost cutting after recording a $22 million loss over the half-year.

Mr Mackenzie says it's been hurt by low copper and uranium prices, but there are more efficiencies to be made.

"We have substantially reduced costs at Olympic Dam and the intention is to continue to work that operation hard," he said.

"In my view it needs to get its cost base if not equivalent to what we're able to achieve at Escondida [a giant copper mine in Chile] to be strongly competitive within the portfolio."

Mr Mackenzie says the company has a strong portfolio of potential projects in the pipeline, and he is aiming to increase internal competition for which projects get funding to proceed.

"On this basis, we believe an average rate of return of greater than 20 per cent is achievable for our portfolio of major development options," he added.

Conservative dividend, debt repayment

The company is paying a fully-franked interim dividend of 59 US cents a share (65 cents Australian), up 2 US cents from the interim dividend last year.

Mr Mackenzie says the payout is in line with the company's established practice.

"When the board have debated that in light of future forecasts then we'll talk to you at the full year but, just to clarify things, for a little while now we've had the practice of effectively putting the dividend up or adjusting the dividend at the full-year and then simply paying the same amount at the half-year, and we are continuing with this practice," he said.

It is using some of its free cash flow to reduce debt from a current level of $US27.1 billion to $US25 billion by the end of the current financial year.

BHP Billiton shares were up just over 2 per cent to $38.80 by 11:25am (AEDT) as investors reacted positively to the result.

On the tax front, BHP says it paid $US29 million ($32.1 million) of Minerals Resource Rent Tax (MRRT) in the period, but this was offset "by the remeasurement of deferred tax assets associated with the MRRT, which reduced taxation expense by US$491 million" ($544 million).