REI Co-op Bike Size Chart: How to Find Your Right Frame Fit

By Caleb Morgan

Updated November 2026

The REI Co-op bike size chart matches your height, inseam, and riding position to a frame size, so you can narrow down which models to test before you ever sit on one. This guide walks you through how to read the chart, measure yourself accurately, check the fit once you have a bike in hand, and avoid the mistakes that send most beginners home with the wrong size. The chart is a starting point, not a verdict, and the steps below show you how to use it well.

What a Bike Size Chart Actually Tells You

A bike size chart is a lookup table. It takes a body measurement, usually your height or inseam, and points to a frame size that brands have found works for riders in that range. Co-op’s chart, like most in the industry, lists sizes in letters (XS, S, M, L, XL) or in centimeters, and some listings also show a suggested rider height range for each size.

Shopping for one? See our guide: 5 Best Road Bike Shoe Size Charts (2026): Expert Picks.

The chart is built on averages. Two people who are both 5’8″ can still need different frames because one has long legs and a short torso, and the other has the reverse. That is why the chart gives you a range to start from, and why the rest of this guide focuses on checking the fit in person or with careful measurements.

Keep in mind that frame size is measured differently across bike types. A road frame’s size is usually the center-to-top of the seat tube, while a hybrid’s size may be listed differently. Always compare the chart for the specific bike category you are shopping, not a general guess.

Step 1: Measure Your Height and Inseam

Before you open the chart, get two numbers right: your standing height and your inseam. Both are easy to measure at home, but small errors add up.

How to measure your height

1. Stand barefoot against a flat wall with your heels, back, and head touching it.
2. Keep your eyes level forward and breathe normally.
3. Mark the top of your head on the wall with a flat object such as a book.
4. Measure from the floor to the mark with a tape measure. Record it in both inches and centimeters.

How to measure your inseam

1. Stand with your back against a wall and place a hardcover book between your legs, spine up, pushed firmly against your crotch.
2. Level the book so it sits flat, like you are sitting on a very thin saddle.
3. Measure from the top edge of the book down to the floor.
4. Take the measurement two or three times and use the average.

Your inseam matters more than height for bikes with a top tube, because your leg length determines how far the saddle needs to sit above the pedals. If you are between two sizes, the inseam usually breaks the tie.

Step 2: Read the REI Co-op Chart Correctly

Once you have your numbers, find the chart for the bike category you want. REI Co-op publishes separate guidance for different styles, so check that you are looking at the correct table before you match your measurements.

A typical chart is laid out with one column for height or inseam and another for the recommended size. Find your height in the first column, then read across to the size. If your height falls between two rows, check your inseam and use that as the tiebreaker. Some charts show a range for each size, so make sure you land inside the range instead of just near it.

Treat the table above as a general guide to the kind of ranges charts use. Always confirm against the exact chart for the model you are considering, because numbers differ between road, hybrid, and mountain bikes.

Step 3: Check Standover Height

Standover height is the clearance between your crotch and the top tube when you stand over the bike with both feet flat. It is the first real-world check of whether a size works, and it matters most for hybrid and commuter bikes that you will mount and dismount often.

1. Stand the bike upright on a flat surface.
2. Straddle the top tube with both feet flat on the floor.
3. Lift the bike gently until the top tube touches your crotch. You want roughly one to two inches of clearance on a road or hybrid bike, and more on a mountain bike, where you may need to jump off the seat.

If you have to rise on your toes to clear the top tube, the frame is too big. If there is a lot of extra room, the frame may be too small for comfortable reach.

Step 4: Assess Reach and Riding Position

Reach is the horizontal distance from the saddle to the handlebars. A frame that is too long forces you to stretch, which strains your back and shoulders. A frame that is too short leaves you cramped and places too much weight on your hands.

Quick riding position test

• Sit on the saddle and rest your hands on the grips or hoods.
• Your elbows should be slightly bent, not locked straight.
• When you look down, your head should feel supported, not craned.
• Your weight should feel balanced between the saddle and the bars.

Saddle height is the other half of the position. With the pedal at its lowest point, your knee should keep a slight bend, roughly 25 to 35 degrees. Most adult riders set the saddle so the leg is nearly straight at the bottom of the stroke without the hips rocking.

Step 5: Factor in Your Riding Style

Two riders with the same measurements can still prefer different sizes depending on how they ride. A commuter who sits upright may want a slightly shorter reach than a fitness rider who leans forward. A trail rider may want a bit more room to move around on the bike.

• Upright and commuting: Lean toward the size that gives a comfortable, relaxed reach.
• Fitness and road: Expect a more stretched position, so check that your back stays comfortable over longer rides.
• Off-road: Prioritize standover clearance and the ability to move your body around the frame.

If you are between sizes, a shorter stem or different handlebar can often adjust reach without changing the frame. Ask a shop about component swaps before you rule out a size.

Common Mistakes When Using a Size Chart

• Trusting height alone. Inseam and torso length change the answer, especially for taller or shorter riders.
• Ignoring the bike category. A road size and a hybrid size with the same letter are not always the same geometry.
• Measuring while wearing shoes. Heels add height and throw off both height and inseam readings.
• Buying the largest size for a growth allowance. A bike that is too big is harder to control and less safe, even if it seems like a good deal for later.
• Skipping the test ride. A chart cannot tell you how a frame feels at speed or over bumps.

Tips for Using the Chart With Confidence

• Measure twice and record both height and inseam before you shop.
• Print or save the exact chart for the model you are considering so you can compare side by side.
• Bring your measurements to a local shop, especially if you are between sizes.
• Ask whether the store offers a fit adjustment or a trial ride before you commit.
• If you are new to cycling, read a general primer first. For example, Women's Bike Size Chart: How to Find Your Right Frame Fit covers the same fit principles across brands.

Recommended gear

A few basic tools make measuring and fit checks much easier at home.

• Flexible tape measure — A soft tape lets you measure height and inseam accurately against a wall without bending the numbers. View on Amazon
• Hardcover book — A flat, firm book is the simplest tool for measuring inseam at home, so keep one ready for the inseam test. View on Amazon
• Bike stand or trainer — A stand lets you adjust saddle height and check the knee angle safely before a ride. View on Amazon

FAQ

Is the REI Co-op bike size chart accurate for every rider?

It is a reliable starting point for most adults, but it is built on averages. Use it to shortlist sizes, then confirm with standover, reach, and a test ride.

Should I measure height or inseam to choose a size?

Use both. Height gives you a general range, while inseam is often the better guide for standover and saddle position. If the two suggest different sizes, the inseam usually deserves more weight.

What is the difference between frame size and wheel size?

Frame size refers to the body of the bike, while wheel size refers to the diameter of the wheels. They are separate measurements, and a chart for one does not cover the other.

Can I ride a bike that is one size too small?

You can, but it will likely feel cramped, with too much weight on the hands and a short reach. Adjusting the stem can help a little, but it does not fix a frame that is too small.

Can I ride a bike that is one size too big?

Riding an oversized bike is harder to control and can be unsafe, especially when stopping or turning at low speed. Choose the size that lets you stand over the top tube with clearance.

How do I know if my saddle height is right?

With the pedal at its lowest point, your knee should have a slight bend. Your hips should stay level on the saddle, not rocking side to side.

Do I need a professional fitting?

A basic fit from a bike shop is helpful, especially if you have knee, hip, or back concerns or ride long distances. If you have a medical condition or ongoing pain, consult a doctor or a qualified bike fitter before making major changes.

Conclusion

The REI Co-op bike size chart gives you a clear starting point: measure your height and inseam, find the matching range, and shortlist the frame sizes that fit. From there, check standover clearance, reach, and saddle height, and take a test ride before you commit. Used this way, the chart saves time and helps you avoid buying a bike that never feels right.

Related reading

• Women's Mountain Bike Size Chart: How to Find Your Right Frame Fit
• Women's Bike Wheel Size Chart: Find Your Right Fit (2026)

About Caleb Morgan

Caleb Morgan is part of our editorial team and reviews and edits our cycling for beginners guides, checking product details against manufacturer specifications and owner feedback.