There are lots of factors to consider when you’re choosing a bike that’s right for you. In addition to choosing the type and style of bike right for your needs, you have to determine the fit. It may seem like one size bike fits all — especially when you discover the adjustable seats. But that’s far from true. To find the right bike size for your body, you have to take into account your height, leg length and the type of bike you’ll be riding. To help you keep your figures straight, use this handy bike size calculator.

There are four general types of bikes out there: road bikes, mountain bikes, BMX bikes and children’s bikes. If you are unsure of what type of bike you have, it is most likely a road bike or a standard children’s bike. These bikes have large, relatively smooth wheels that are ideal for riding along paved roads.

Mountain bikes are more compact than road bikes. Their frames are thick and stocky to handle the bumpy, demanding terrain of off-road biking. The wheels are thick with wide tread to grip the ground when things get rough and the handlebars sit cross-wise for easy gripping as you bump around. Mountain bikes also go by a few other names:

• All-terrain bikes
• 29ers
• Downhill bikes
• Freeride bikes

BMX bikes are smaller and more compact still than mountain bikes. These small, light bikes are designed to make stunts and tricks easy to pull off. Their wheels are very thick with visible, chunky tread. Their frames sit slightly lower than those of mountain bikes to facilitate acrobatics.

Once you determine the type of bike you’re considering, select it from the pull down menu on the bike size calculator.

Measuring your height in inches can be tricky. If you have a partner, stand straight without shoes and have your partner measure you with a metal measuring tape. If you’re alone, stand straight against a wall and use a pencil to mark the height of the top of your head on the wall. Then measure the length from that point to the floor.

Measuring tapes measure in feet and inches. For this bike size calculator, you will need to convert your measurement into inches with a little multiplication. For example, if you are 5 feet 4 inches tall, multiply the feet by 12 to get 60 inches. Then add the existing inches to get 64 inches. Enter those inches into the height space.

Your inseam is the distance in inches that runs from the bottom of your foot to the top of your inner thigh. Again, this measurement is best taken with the help of a friend and a pair of snug pants. Stand in a relaxed position with your feet hip distance apart.

Start the measuring tape at the inside of your foot just below the ankle. Then extend the tape all the way to the top of the thigh where it meets the pelvis. Record the measurement in feet and inches and then convert the feet into inches.

It is possible but difficult to take your inseam measurement yourself. Marking the height of your inseam on a wall won’t work because it doesn’t take the angle of your stance into account. If you can, extend the measuring tape from your inner foot to your inseam without bending your leg, then take the measurement. Propping your heel up on a chair may help you reach. Keep in mind that the measurement is only useful if you can keep your knee straight while you measure.

Once you have the type of bike and measurements on hand, enter them into the calculator and hit “Calculate!” You will get a measurement in inches that you can take to any bike shop or use while shopping online. Bikes within one or two inches of this measurement on either side are suitable for your size.