Bike Frame Size Calculator: Height, Inseam and Standover

Your frame size comes mostly from two numbers, your height and your inseam, and the result only means something for the specific bike you are looking at, because a medium from one brand or bike type is not another’s medium. The calculator below checks your measurements against Giant’s published size bands for a hybrid, an endurance road bike and a hardtail mountain bike, and shows how much standover clearance each size would give you.

Frame size calculator

Enter your height and inseam in inches, both measured barefoot (the next section shows how). The size bands and standover heights come from the sizing tables on Giant’s own product pages for the Escape 3, Contend AR 3 and Talon 29 3, read on October 27, 2026. They are a worked example: Giant itself calls its sizing a reference only, and other brands draw their bands differently.

How to measure your height and inseam

Trek, which sizes its bikes mainly by height and inseam, describes the inseam measurement like this: put on cycling shorts and stand barefoot with your back straight against a wall, then use a ruler to measure from your crotch straight down to the floor. Giant’s sizing tool asks for height measured without shoes (barefoot or in socks), standing straight against a wall.

1. Measure height barefoot against a wall, heels and back against it, and mark the top of your head.
2. Measure inseam barefoot in cycling shorts, from the crotch down to the floor, with your back straight against the wall.
3. Write both down in the same units and measure twice. A half-inch error can move you into the next size band.

What the size bands look like

This table is the data behind the calculator. The standover heights are Giant’s published numbers for each size; reach and stack are in inches.

Model	Size	Height band	Standover (in)	Reach (in)	Stack (in)
Giant Escape 3 (hybrid)	S	5’3” to 5’7”	28.1	16.0	21.2
Giant Escape 3 (hybrid)	M	5’7” to 5’11”	29.7	16.1	21.9
Giant Escape 3 (hybrid)	L	5’11” to 6’3”	31.5	16.4	23.0
Giant Escape 3 (hybrid)	XL	6’3” to 6’7”	33.1	16.7	24.1
Giant Contend AR 3 (endurance road)	S	5’5” to 5’9”	29.9	14.8	22.0
Giant Contend AR 3 (endurance road)	M	5’7” to 5’11”	30.8	15.0	22.6
Giant Contend AR 3 (endurance road)	M/L	5’10” to 6’2”	31.9	15.1	23.4
Giant Contend AR 3 (endurance road)	L	6’0” to 6’4”	32.6	15.4	24.2
Giant Contend AR 3 (endurance road)	XL	6’2” to 6’6”	33.7	15.7	25.1
Giant Talon 29 3 (hardtail mountain)	S	5’4” to 5’8”	28.6	15.7	23.7
Giant Talon 29 3 (hardtail mountain)	M	5’7” to 5’11”	29.9	16.5	24.1
Giant Talon 29 3 (hardtail mountain)	L	5’10” to 6’2”	31.4	17.1	24.8
Giant Talon 29 3 (hardtail mountain)	XL	6’2” to 6’6”	32.8	17.9	25.3

Two things stand out. Neighboring size bands overlap or touch on every model, and on the Contend AR 3 a 6’2” rider (74 inches) falls into three sizes at once: M/L, L and XL. And the size letter does not carry across bike types: a medium has a reach of 15.0 inches on the Contend AR 3, 16.1 on the Escape 3 and 16.5 on the Talon 29 3.

If you fall between two sizes

Trek’s mountain bike sizing guide treats height as the easiest starting point, then tells riders to choose up or down by riding style and proportions. A longer reach suits riders who plow through rough terrain, a shorter reach suits playful riders, and a long torso or arms may fit a longer reach better. It also says reach is the most useful number for comparing sizes across brands, more than standover height or seat tube length, since most trail riders spend time standing on the pedals. On a road or hybrid bike the same logic applies: in the table above, each step up in size adds reach and stack, so the larger frame puts the bars farther away and higher.

A quick decision table

Your situation	Lean toward	Why
Standover clearance is zero or negative on the larger size	The smaller size	You cannot straddle the frame with both feet flat
Long torso or long arms for your height	The larger size	More reach, per Trek’s guidance on torso and arm length
Short torso or short arms for your height	The smaller size	Shorter reach, per the same guidance
Want stable, planted handling on rough ground	The larger size	Longer reach suits riders who plow through rough terrain
Want a playful, easy-to-move bike	The smaller size	Shorter reach suits playful riders

After you pick a size

Check that you can straddle the bike with both feet flat and a little room over the top tube, then adjust the saddle (see how to set seat height) before judging the fit. Small reach changes come from the stem and saddle position, and the common bike fit problems guide shows which pain points to a frame that is wrong rather than a setup that needs tweaking. For specific bike types, see how to measure a mountain bike frame, what size gravel bike frame you need, and who a 24-inch bike fits. Whatever size the calculator suggests, compare the maker’s own chart for the exact model before buying, and ride it if you can.