If I have lived in my home l less than 2 years and have to relocated for employment, how would the capital gain be calculated?

If filing as Single you would receive a partial exclusion of $250,000 * 18/24 = $187,500

IRS Publication 523 Selling Your Home page 6 - https://www.irs.gov/pub/irs-pdf/p523.pdf#page=6

Work-Related Move
You meet the requirements for a partial exclusion if any of the following events occurred during your time of ownership and residence in the home.
• You took or were transferred to a new job in a work location at least 50 miles farther from the home than

your old work location. For example, your old work location was 15 miles from the home and your new work

location is 65 miles from the home.
• You had no previous work location and you began a new job at least 50 miles from the home.
• Either of the above is true of your spouse, a co-owner of the home, or anyone else for whom the home was

his or her residence.

there is a safe harbor provision that if complied with allows you to claim the partial exclusion for change in place of employment that the IRS can not challenge:

the new place of employment is at least 50 miles farther from the taxpayer's old home than the former place of employment was.

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