$900,000 - $250,000 = $650,000 long term capital gain (reduced by any expenses of sale, e.g. broker commission). You may exclude $250,000 ($500,000 if married filing jointly)
Long term capital gain (LTCG) are partially taxed at 0%, 15%, 20% and/or 23.8%, depending on your other income.
Try this tool https://turbotax.intuit.com/tax-tools/calculators/taxcaster/?s=1. Enter your regular income first to see the regular tax. Then add the sale to see the effect.
