Estimate the tax on a capital gain. In Canada, 50% of your gain is added to taxable income and taxed at your marginal rate (federal + provincial).
Canada has no separate capital gains tax rate. Instead, a portion of your gain — the inclusion rate, currently 50% — is added to your taxable income and taxed at your marginal rate (federal plus provincial). So if you realise a $50,000 gain, $25,000 is added to your income; the tax depends on what bracket that lands in.
The federal government proposed raising the inclusion rate to two-thirds on gains over $250,000, but that change was cancelled, so 50% applies to everyone. Your principal residence is generally exempt, and gains earned inside a TFSA or RRSP are not taxed. Capital losses can be applied against gains in the year, carried back three years, or carried forward indefinitely.