Updates with Q1 margin in paragraph 2, shares in paragraph 4, segment details in paragraphs 7 and 8.

By Leo Marchandon

April 24 (Reuters) - The world's biggest lighting maker Signify LIGHT.AS reported a 12% drop in its quarterly nominal sales to 1.27 billion euros ($1.48 billion) on Friday, dragged by the costs of converting weak U.S. dollars into euros.

The Dutch group confirmed its full-year guidance for a core profit margin, or proportion of earnings before interest, taxes and amortisation to sales, of between 7.5% and 8.5%. The margin was 6.5% in the first quarter, down from 8% a year ago.

Signify declined to provide a sales forecast for the year.

Its Amsterdam-listed shares were down 1% at 0900 GMT, reversing course after rising around 2.5% initially.

Active in more than 70 markets with brands such as Philips, Philips Hue and Color Kinetics, the company faces sluggish global lighting demand while navigating a recently launched restructuring programme. A strategic portfolio review is also underway, aimed at repositioning Signify for growth.

Its net income plunged to 8 million euros from 67 million euros a year ago, mainly due to restructuring charges of 63 million euros linked to the 180-million-euro cost-cutting plan.

The Professional segment, Signify's largest, saw nominal sales fall 11% to 839 million euros, hurt by a 7.3% currency impact and continued softness in public projects across Europe and the United States.

The Consumer segment, which sells Philips Hue smart lights, posted an 11.5% sales drop to 276 million euros, as inventory adjustments by retailers weighed on volumes despite strong consumer appetite.

At the end of March, Signify had a workforce of 26,008, down by 12% from 29,697 a year earlier. Most of the job cuts were tied to factory roles as production volumes dipped.

($1 = 0.8563 euros)