bicycle repair?

You'll need either a 9/16" wrench or a 6mm or 8mm allen wrench most likely. There are some 5/8" pedal wrench flats but they're not very common.

The left-side pedal is reverse-threaded to keep it from unscrewing while you ride the bike.....the right pedal is a normal thread.

If you don't see wrench flats on the pedal axle next to where it enters the crankarm, then look on the back side (the end) of the axle and you should see a place to put an allen wrench.

An easy way to remember which way to turn your wrench is to point the crankarm forward, and then point the wrench backwards and apply pressure. If you don't have a chainring guard on the front gears, wear a leather glove to protect your hands when you loosen the right-side pedal, just in case the wrench slips or the pedal breaks free suddenly.

If you can't get them to budge, try a little WD-40 or rust penetrant on the threads, let it sit awhile, tap it with a screwdriver handle a few times, and then give it another go.

Hope this helps!

You'll need a 15mm pedal wrench. Sometimes a regular 15mm wrench will work, but most pedals have a narrow slot and require the special tool.

Always remember that the left (non drive side) pedal has a reverse thread, and must be loosened by turning it clockwise.

Check this source link for a video demonstrating the removal and installation procedure.

One needs a wrench that is made for that purpose or a box wrench. The usual size is a 15mm. The right sided pedal gets unscrewed counterclockwise while the left is unscrewed clockwise. Once the pedal has started to loosen turn the crank forward while the wrench is still in place making it come off faster.

5/8" wrench on the wrench flats on the pedals nearest the crank. Pull towards the back of the bike on both sides. The left pedal (non-drive side) is threaded reverse of normal so the pedals don't unscrew themselves while riding.