Losing even a single employee can be decimating to your productivity as a team. Based on the numbers you provide, we're able to calculate your turnover rate. However, to fully understand how big of an impact losing an engineer will be, we'll need to make some educated guesses about the replacement and ramp up costs for engineers in your company.
It costs 75% of an employee's salary to replace an engineer. Factoring into this percentage is the recruiting and sourcing costs, possible fees for external recruiting agencies, changes in price to benefits, and the possible issuance of new stock options or RSUs in addition to those outstanding. In extreme cases, the cost can be more than double!
Onboarding will take four and a half months until the engineer is fully effective. Interviews with top Silicon Valley companies estimate that new employees spend about half of their time during the first three to six months at a new company learning the systems, processes, and tools required for them to be effective. Given the large variance in responses for onboarding time, 4.5 months is exactly halfway between the extremes.
These two values, paired with data from PayScale for engineering salaries around the United States gives us insight into the real cost of losing a single engineer. With data from Gallup (1, 2, 3) about 73% of employee attrition can be attributed in some manner to growth and development, wether it's a bad leader or a lack of opportunity.