The question you opened
Seventy eight thousand, per hour
A contract pays 78,000 dollars for a year of work, and the year holds 2,000 working hours.
What does that come to an hour, in dollars?
$39
Dividing by 2,000 is dividing by 1,000 and then by two. Seventy eight becomes 39, so the rate is 39 dollars an hour.
Two thousand hours is the standard shorthand for a working year: 40 hours a week for 50 weeks. Dividing by 2,000 is dividing by 1,000 and then halving, so 78,000 becomes 78 and then 39. The rule reduces to a sentence: halve the number of thousands. It runs in reverse just as easily, which is where it earns its keep. A rate of 60 dollars an hour is 120,000 a year. A rate of 25 is 50,000.
Anyone comparing a salary offer with a freelance rate can do the conversion during the conversation rather than after it. The 2,000 figure is deliberately generous to the employer side of the comparison. A real year holds about 2,080 working hours before any leave, and a contractor with four weeks off works closer to 1,900. Using 2,000 keeps the arithmetic clean and lands within about 5 percent, which is well inside the noise of any offer.
The comparison is incomplete in one important way. An employee at 39 dollars an hour also receives paid leave, employer contributions, insurance, and equipment. A contractor billing 39 receives none of those and pays their own idle weeks, so the honest rule of thumb is that a contract rate needs to be substantially above the equivalent salary rate to match it. Many people use a factor between 1.3 and 1.5.
The transferable piece is the divide by a thousand and halve pattern itself. Anything per 2,000 units works this way: fuel per 2,000 kilometres, cost per 2,000 impressions, servings per 2,000 calories. Spotting a round divisor and turning it into two trivial steps is most of what fast arithmetic actually is.
Technique: Halve the thousands