Google the population of your city. Count how many non-Christians came to faith as a result of your ministry/church/whatever's efforts in the last year.
Divide the population by the the number of new believers.
That's how many years it would take to reach your city.
(And... that doesn't account for population growth through nett births-deaths, or through net migration.)
Now: how many other churches are there in your city, and how many are they likely to have grown by in the past year?
Sum, do the calculation over again.
Now: is what we're doing enough?
"What's it going to take?"