Grocery giant Woolworths has posted $30.7 billion in first-half sales with the retailer saying it had placed a greater focus on its core business.

The company said its sales for the 27 weeks to December 30 were up 3.2 per cent on the previous corresponding period.

Chief executive Grant O'Brien said the result was pleasing but more work was needed.

"This solid first-half result is a reflection of the sharpened focus on our core businesses and better meeting our customers needs," he said in a statement.