What a 20-hour contract really costs: it's not 900 euros

Hiring on a 900 euro monthly budget doesn't cost 900 euros a month

How much do you actually need to put on the table to hire someone for 20 hours a week? The short answer: more than the gross salary suggests. The long answer depends on three variables almost nobody looks at at the start —the applicable collective agreement, the job category and the type of contract— which, according to the calculations discussed by participants in the conversation, push the final cost between 30% and 100% above the salary. With a monthly budget of 900 euros, the margin narrows to the point where the relevant question is no longer how much the company pays, but how much the person signing actually takes home.

What you pay on top of the gross salary

The gross salary is only the first layer. On top come the employer's social security contributions, which for an ordinary permanent contract run at around **32.10%** of gross pay according to the breakdown circulating in the conversation. But there's more: extra pay, holidays, possible sick leave, severance pay, accounting services, training and occupational risk coverage. Hence the most repeated —and most prudent— rule of thumb: multiply the salary by two. Or even by three, if you want to sleep soundly.

The problem is that this multiplier isn't a formula, it's a cushion. A more precise calculation requires going into detail: the applicable agreement, annual working hours and job category. For an office worker in Madrid with an annual working year of **1,765 hours**, the cost per hour varies by category: **9.16 euros** for a university graduate, **8.85** for an associate degree holder and **6.21** for an assistant. Employer contributions are added on top of these amounts. The difference between the highest and lowest category is almost 50% of the cost, and that's before factoring in the type of contract.

The specific case: 20 hours and an 850 euro budget

Applied to the example raised in the query —remote blog writing work, part-time, 850 euro cap— the range opens up. A fixed-task contract at 20 hours a week can fit the budget, but the category is what matters: with **6.21 euros/hour** in salary cost plus contributions, the resulting gross pay falls in the range of **650 to 690 euros**, leaving a net of "just over six hundred". With higher categories, the 850 euros don't stretch far enough.

The question hovering over the whole calculation is an uncomfortable one: an efficient contract for whom? What lowers the employer's cost —a low category, reduced hours, a temporary contract— is exactly what makes the worker's situation precarious. And vice versa. There's no formula that optimizes both at once, however much you try to square the circle in a spreadsheet.

The fine print everyone forgets

The type of contract, the city, the sector's collective agreement and the category are the four parameters that determine the real cost. Without them, any figure is a shot in the dark. Spain's Social Security system publishes contribution tables, but that doesn't answer the question of how much a specific contract costs: that requires combining the collective agreement with the contribution base and the applicable rate. It's a job for an advisor, not an online calculator.

The conclusion, if you want one: a 900 euro budget doesn't equal a 900 euro salary. It equals a gross salary of between 650 and 700 euros at best, with a net that rarely exceeds 650. The rest goes to the system. And anyone who doesn't factor that in will get a surprise with the first payslip.