Check out the calculator on the CRA's website: https://www.canada.ca/en/revenue-agency/services/child-family-benefits/child-family-benefits-calcula...
They call it the family benefit calculator but if you follow the steps, it will help you figure out your WITB eligibility too. As of today, it' doesn't appear to have been updated for the 2017 tax year yet, but the 2016 calculator should give you a reasonable estimate.