Markup and margin, converted both ways.

Both measure the same profit. Markup compares it with what the job cost you; margin compares it with what the customer paid. A job that costs $100 and sells for $150 makes $50 of profit: a 50% markup and a 33.33% margin. For any profitable job, the margin is the smaller number.

A 100% margin would mean the whole price is profit, which only happens when the cost is zero. As the margin gets closer to 100%, the price needed climbs without limit, so the calculator only accepts margins below 100%. Markup has no ceiling: a 200% markup is simply three times the cost.

Either works if you use it consistently. Markup is easier to apply, because it starts from the cost you already know. Margin is easier to compare across jobs, because it shows what share of each dollar you keep. The mistake to avoid is choosing a target margin and then applying it as a markup, which prices every job too low.

Gross. It compares the price with the direct cost you entered and says nothing about overhead. A job can show a healthy gross margin and still lose money once insurance, vehicles, the office and your own time are paid for.