The wage is not the cost. A painter on $35 an hour costs the business considerably more once statutory on-costs, paid leave and non-productive time are counted — and quoting off the wage is the most common reason a job that looked profitable was not.
A casual carries a loading on the wage instead of paid leave, so the arithmetic differs by worker type. A subcontractor invoices their own rate and carries their own on-costs, which is a different calculation again.
Most jobs are not run by one worker type. The calculator takes a crew — painters, a leading hand, apprentices, casuals, subbies — with headcount and pay for each, and weights them into one loaded rate by headcount. That single rate is what a costed estimate multiplies hours by.
Terminology follows the market: leading hand in Australia and New Zealand, lead hand in Canada, foreman in the United States and the United Kingdom.
The loaded rate is what an hour costs you. What you charge is that cost divided by one minus your margin — not the cost plus a percentage. Cost ÷ 0.70 is a 30% margin; cost × 1.30 is a 23.1% margin, and quoting the second while believing the first is a steady, invisible loss.