* Q4 orders up 14.5 pct, its slowest pace in 6 qtrs
* Sees 2018 adj gross margin 23.75-24.25 pct vs 24.80 pct in 2017
* Shares down 5.2 pct in light premarket trading (Adds details on forecast, background, estimates, share price)
Dec 5 (Reuters) - Toll Brothers Inc on Tuesday posted a quarterly profit and revenue that missed analysts' estimates, and reported its slowest order growth in six quarters, sending its shares down in pre-market trade.
The U.S. luxury homebuilder also forecast a decline in its full-year 2018 adjusted gross margin. The company's shares were down 5.2 percent at $48 in light premarket trading.
A robust job market has supported demand for housing in the United States, but homebuilders are not fully able to benefit from it due to supply constraints such as higher labor and raw material costs.
Orders, a key metric of future revenue for homebuilders, rose 14.5 percent to 1,979 homes for Toll Brothers in the three months ended Oct. 31, its slowest pace in six quarters.
The company, which mainly builds single-family homes, expects fiscal 2018 adjusted gross margin of between 23.75 percent and 24.25 percent, compared with 24.80 percent this year.
The homebuilder forecast full-year revenue of between $6.24 billion and $7.48 billion, compared with $5.81 billion this year.
For the first quarter, the company expects to sell between 1,300 and 1,500 units at an average price of between $820,000 and $840,000.
Toll Brothers introduced a new line of homes with lower prices and quicker delivery times to tap rising demand from millennials who are starting families, a move that has weighed on the company's average prices.
The company said the average price of homes sold increased to $836,600 in the latest fourth quarter from a year earlier, while the number of homes sold rose 9 percent to 2,424.
The company's net income rose to $191.9 million, or $1.17 per share, in the quarter, from $114.4 million, or 67 cents per share, a year earlier.
The year-ago quarter was hit by a $121.2 million warranty charge.
Revenue rose 9.3 percent to $2.03 billion.
Analysts on average had expected a profit of $1.19 per share and revenue of $2.08 billion, according to Thomson Reuters I/B/E/S.
Up to Monday's close, the company's shares had risen 63.4 percent this year. (Reporting by Arunima Banerjee in Bengaluru; Editing by Saumyadeb Chakrabarty and Shounak Dasgupta)