Here’s a classic grammar conundrum:
Less or fewer: Which one should you use?
In general, use fewer for individual units and less for a bulk amount.
I have fewer pencils than pens.
The store sold fewer iPads than iPhones.
I have less money than they do.
Joe weighs less than John.
Sometimes, a group of units is considered a whole, rather than the individual units that make up that whole. This usually happens when units of measure are used in “less than” constructions.
I walked less than 5 miles today.
(But: I walked fewer miles than you.)
I have less than $50 in my pocket.
(But: I have fewer bills in my pocket than I did yesterday.)
Now, for a tricky one: Which is correct?
Now that this is done, I have one less task to complete.
Now that this is done, I have one fewer task to complete.
Well, the first one sounds right. And it is (although some people will dispute this based on the logic above). Although tasks are individual units, “task” is singular here, and “fewer” is used only in the plural construction. But the best option here is to rewrite it: Now that this is done, I have fewer tasks to complete.