Brompton Bike Size Chart

1. 01

   One frame covers 140–203 cm

   Brompton publishes a rider height range of 140–203 cm. The frame does not change. The seatpost length and the handlebar rise change. The chart therefore has one size, and the fit depends on your height and your inseam.

2. 02

   Choose the seatpost by inseam

   Brompton publishes an inseam range of 66–99 cm across its seatpost options. The standard post is the shortest. The extended post adds 60 mm. The telescopic post is the longest. Measure inseam barefoot, floor to crotch, with your back against a wall. Compare it with the range for the post you are buying, then leave room to raise the saddle.

3. 03

   Choose the handlebar by posture

   Brompton offers low, mid, and high handlebars. Low sets the longest reach and the most forward posture. Mid raises the bars for an upright ride. High raises them further for the shortest reach. The bar choice changes the ride, not the frame size. Pick the posture you will hold for the length of your commute, then confirm the bar type on the model you buy.

4. 04

   The G Line adds three sizes

   The G Line uses three sizes: S, M, and L. Each size has a different stem length, seatpost length, and reach. Brompton publishes a reach figure for each one on the G Line page. The C Line, P Line, and T Line keep one frame. Read the G Line listing on its own spec sheet before you compare it with a C Line.

5. 05

   A longer seatpost changes the folded saddle height

   A longer seatpost leaves the saddle higher when the bike is folded. Brompton sells a telescopic post that keeps the folded saddle height close to the standard post. Measure the folded height with the saddle at your riding height. A telescopic post drops in two sections, so the folded package stays close to the standard post. If you store the bike under a desk or on a train rack, check the folded height on the spec sheet, not the rider height range.

6. 06

   16-inch and 20-inch wheels change the fit

   Brompton builds the C Line, P Line, and T Line on 16 inch wheels and the G Line on 20 inch wheels. A larger wheel rolls over rough ground with less effort. It also changes the folded size and the weight. A rider who lifts the bike onto a train every day checks the folded size and the weight on the spec sheet. A rider who rides gravel paths checks the tyre clearance and the brakes.

7. 07

   Set the saddle before the handlebar

   Fit the saddle height first. Sit on the bike, put the ball of the foot on the pedal at the bottom of the stroke, and set the knee to a slight bend. Note how much post shows above the frame. Then set the handlebar height. A low bar sets a forward posture. A high bar sets an upright one. Raising the bar shortens the reach. Lowering the bar lengthens it. Confirm the seatpost clamp holds before the first ride.

8. 08

   Check the bike at the shop

   Unfold and fold the bike once before you pay. Check that the frame hinge closes with a firm click, that the seatpost clamp holds the saddle at your height, and that both brake levers reach the bar with two fingers. Check the tyre pressure printed on the tyre. Ask the shop to set the saddle height and to record the post length for you.

9. 09

   Measure before you order

   Take height and inseam with shoes off. Compare the inseam with the seatpost range, then confirm the handlebar type. Keep the minimum insertion mark inside the frame. A rider at the top of a seatpost range needs the next post, because the saddle clamp adds height above the post.

Need the full sequence, including between-size rules? See how to choose a bike size.