"estimate of when" is a grammatically correct phrase and can be used in written English.
It is used to indicate a prediction or estimation of a specific time or event. Example: The meteorologist gave an estimate of when the storm would hit the city.
They did not offer an estimate of when it would be under control.
The press briefing did not provide any new details or even an estimate of when the investigation might be completed.
When asked for an estimate of when the Russia inquiry might wrap up, Mueller responded, "I honestly can't say.
Crews were out assessing the damage but could not provide an estimate of when people would get power back.
IN a secret report of Sept. 20, 1949, the Central Intelligence Agency gave its best estimate of when Moscow would have the atom bomb, ending the American monopoly.
JF Do we have some sort of estimate of when I'm finally going to be able to see her? New York State's Personal Attorney Jeremy?
The Postal Service frequently cannot give customers an accurate estimate of when their mail will be delivered, a government report said.
And his estimate of when that day might come is sobering, despite CNN.com's financial buoyancy: 10 to 20 years from now.
The findings, the village said, seemed all the more credible because the English experts set their date without knowing the village's estimate of when the house was built.
By studying the tortoises' current genetic makeup, the scientists were also able to come up with an estimate of when this genetic bottleneck occurred.
Measuring the polarization more accurately allowed the Wilkinson team to refine its previous estimate of when the stars first turned on.
