Here is what you will need: a shallow bucket, adjustable wrench, screwdriver or drill, and perhaps a pair of helping hands to carry the countertop. Optional: a hammer and chisel.
Step 1: Turn off the water to the sink. A bathroom will generally have 3 pieces of plumbing beneath the sink: hot water, cold water, and sink drainage. The hot and cold water are off when they are perpendicular ( like an L) to the line. You can check that you’ve done this correctly simply by trying to use the sink. If no water comes out, you were successful.
Step 2: Disconnect the drain. The drain is the vertical piece that connects your sink to the pee trap (the U piece which prevents smells and vapors from returning to your bathroom from the sewer system). You do not need to remove the pee trap. Disconnect the drain just above the pee trap U by turning the plastic nut counterclockwise until it is loose. There might be water in the drain at this point, Make sure your bucket is beneath the drain to catch any water.
Step 3: At this point, your sink is disconnected. Next, you will need to remove your countertop. Your countertop is held onto your cabinet by screws at each corner. Remove these screws. The photo below shows the triangular pieces that come standard on cabinet bases. These four triangles are where you should find the screws to remove.
Step 4: Your countertop might also have a back splash attached. These may, or may not, be attached to the wall. You can tell easily by attempting to lift the countertop off. If the countertop comes loose, you can now lift it off. But be careful. Your sink is still connected to the countertop. Lift vertically until the sink drain is clear and then remove the countertop. If your back splash is attached, you are now done and ready to install a new countertop!
Step 5: If your back splash is attached to the wall, you can peel the front face of Formica off to see if there are screws visible. Contractors are apt to either glue the back splash to the wall or utilize a screw. If there are only screws, you can remove them. If there are no screws, you can pry the back splash off by hammering a flat tool between the back splash and wall. This step might not be necessary since back splashes are often just glued in place and can be removed simultaneously with the countertop.
Congratulations! Your countertops are now removed. Next, you can install a new countertop and update the aesthetic of your bathroom. Be on the lookout for a post on DIY Butcher-block counter tops!