Katy Bourne said that the 3,213 officers in Sussex Police in 2010 was an ‘unsustainable’ number.
Since then the force has made nearly £90m in savings, with the number of officers reduced to 2,587 (as of March last year).
Plans were announced this year to boost numbers by 200 over the next four years.
Mrs Bourne said: “There will be 200 more [officers] by 2022 than we currently have.
“Sussex Police is a reasonable-sized force, so you roughly have 130-150 people a year leave the organisation. They’ll retire or they’ll move elsewhere
“So effectively over the next four years 600 people will probably leave for whatever reasons and in order to get 200 more than we currently have we need to recruit 800.”
Asked about 2010 police numbers, which were considerably higher even with the 200 extra officers, Mrs Bourne said 2010 was ‘unrealistic’.
“If you go back to 2010, policing had been resourced for quite a period of years.
“It was probably at its highest resourced ever and was unsustainable.
“I doubt it will ever get back to that, not in my lifetime.
“The public have said ‘we want more visible policing it makes us feel safe’ and I absolutely agree.
“So we are investing in extra police officers.
“Would I like more? Of course I would. But we have got to be realistic within the budget we’ve got.”
She said the crime landscape has changed since 2010, with police having to prioritise.
“I’ve seen the police now respond to a different nature of crime that perhaps wasn’t even around 10 years ago.
“If you think of online crime, that accounts for huge demand on police time now.
“Child abuse and child exploitation – as a country we had cases [before 2010] but we didn’t really understand the significance.
“Any public sector organisation has to prioritise. But it’s very difficult for the police because they are dealing with victims of crime who are very vulnerable.
“I have a huge amount of respect for police officers and police staff. The real dedication that they give to their jobs is incredible, it’s unparalleled.”