Divide your rear sprocket into your front sprocket. Like 25x9. 25 divided by 9 = 2.77. so 2.77 to 1 is the drive ratio. If you go with a smaller sprocket like a 24 in the front but still a 9 in the back, you are lowering the gear ratio to 2.66 to 1. So your bike will be slower but easier to pedal.
If you go with a 25 in the front and a 10 in the back, you end up with a 2.5 to 1 ratio.
Don't confuse gear ratio with gear inches, that's a calculation including the wheel and sometimes the circumference of the tire.
It will if you have bmx (or bmx style) cranks.
Of course it will, but in my opinion freewheels arent the best
Not a sprocket only, but you can buy a 23-tooth freewheel that should fit.
i would assume you have cranks with a built in sprocket, if this is the case, you can't
the easiest way is to go to your local bike shop
change out the hub
Sprocket size will b 16T & 39
There are two different hub designs for BMX, freewheels and freehubs. You need to know what you have if you want to replace the sprocket by the rear wheel.
You might have to either lengthen or shorten the chain, depending on if you're getting a bigger or smaller sprocket.
Bmx's don't come in sizes. They are all one size.
630 pitch, 96 links
Guessing an 11T cog (sproket), maybe a custom 10T.