Bike fit measurements: record a repeatable bicycle setup
A practical measurement checklist: name the saddle and cockpit points, choose a bottom-bracket datum, repeat readings and keep an honest record without inventing fit targets.
Published 8 October 2026 · OpenBikeFit
Measurement field guide
One origin. Two components.
BB centre = origin · X forward · Y up
Bar X 480 mm · Bar Y 605 mm
Fictional points; schematic, not to scale.
On this page
Record before interpreting
Use the free blank worksheet
Keep the physical reference, units and repeated readings together without creating a saved bike.
Open toolA bike fit measurement sheet is useful when it lets you find the same point again. A list of numbers without references cannot reliably describe the position that produced them. This guide records the bicycle as it is; it does not tell you where your saddle or hands ought to be.
You can follow the checklist on paper without opening a bike database, recording a rider or entering contact details. If you later choose a local passport, copy your measured values and their references rather than the fictional examples below. Keep the original readings until you have checked the finished record.
Separate the three kinds of measurement
Body height and inseam are dimensions of a person. A formula can use them to produce a starting estimate, but that estimate does not establish the current bicycle position. A bike coordinate describes a named physical point. A camera result estimates movement in the image under its recording conditions. None of these is an automatic replacement for either of the others.
Write the intended task at the top of your record: preserve the existing setup, compare two measured bikes, or verify a declared component change. For the first task, no adjustment is needed. Do not loosen parts just to complete a measurement sheet. If a point is inaccessible or the bike cannot be supported securely, leave the reading unrecorded and use appropriate help.
Set the bike and coordinate datum
Support the bicycle upright on a stable surface with both wheel axles at the same height. A trainer or stand can change wheel height, so do not assume its floor position provides a level bicycle. Record how you established the axle alignment and how the bike was supported. A different tilt changes the relationship between the frame and gravity.
For BB-relative coordinates, the origin is the centre of the bottom bracket, around which the crank rotates. X is the horizontal component, positive toward the front wheel. Y is the vertical component, positive upward. These are components, not tape lengths along a diagonal. A plumb reference can establish a vertical through a point; a level reference can help separate horizontal and vertical readings. Record the tools and the side used.
Fictional arithmetic: the BB centre is 270 mm above the same floor datum and the handlebar-clamp centre is 875 mm above it. Bar Y is 875 − 270 = 605 mm, not 875 mm. A separate horizontal reading puts the clamp 480 mm forward of the BB. The recorded point is therefore Bar X 480 mm, Bar Y 605 mm. These numbers illustrate subtraction, not a recommended cockpit.
Name the saddle endpoint before measuring
Saddle height needs an endpoint on the top surface as well as a BB origin and a stated path. A direct straight-line distance to a marked reference is not the same quantity as its vertical Y component. A nose-based setback is not a setback to a different point on the saddle. Write the endpoint before picking up the tape; otherwise an apparently precise reading can answer the wrong question.
Include the saddle make and model, the selected top-surface point, its location relative to a reproducible mark, the tilt reference and whether the saddle was loaded. Use the same declared condition when checking it later. Ergon's published BMR convention is an example of a repeatable model reference, not a rule that every saddle shares. A different saddle may require a different documented convention.
Record the cockpit as named points
Frame stack and reach end at the frame's upper head-tube reference. They are not your handlebar or hood coordinates. A bar-clamp centre and a chosen hood point are separate physical endpoints. Stem, spacer, bar and control declarations explain how a frame can produce a cockpit; they do not turn a manufacturer's frame table into a physical measurement of your installed controls.
List the handlebar model, stem length and stated angle convention, spacer stack and the exact left/right hood references when relevant. For any drop measurement, say which saddle point and which bar point form the vertical difference. For reach, say whether it is horizontal or a direct tape distance. Keep the units visible rather than relying on a field name to carry the definition.
Repeat readings and retain the disagreement
Remove and reposition the measuring tool before taking the next reading, then find the same declared point again. Re-reading an unchanged tape position only checks the display. Record the individual values, not just a selected favourite. If readings disagree, check the endpoint, bicycle alignment, tape path and tools before treating the difference as a bicycle change.
A fictional 740, 743 and 741 mm series has a 3 mm span between its lowest and highest readings. That span describes this series, not instrument accuracy or a confidence interval. Writing 741.33 mm does not create sub-millimetre certainty. Keep any rounding consistent and do not use an average to disguise a wrong reference or an unstable measuring method.
Finish a usable measurement record
The minimum useful entry contains a date, component identity, named point, datum, units, direction convention, method, individual readings and limitations. Mark missing values Not measured. Do not copy a calculator result into an installed field, copy a diagram's fictional coordinate onto the bike, or label a measurement as approved compatibility, installation or comfort.
The free blank worksheet provides a paper-first option. My bikes provides an optional local passport, and the setup-card tool can present one saved bike with its references. These are distinct choices: reading this guide saves nothing, visiting the worksheet creates no bike, and a saved passport requires your explicit action. Downloaded or printed copies may remain or sync outside the site. Keep them in your own controlled workflow.
Use the record for the right next task
To compare frames, first understand the difference between a frame endpoint and your measured bar-clamp target. To compare saddles, resolve the endpoint convention before comparing a height or setback. To judge a small claimed change, look at repeated readings under the same protocol. The three related guides below expand those tasks instead of sending every reader to a body-measurement calculator.
A workshop hand-off should state what was actually measured and what still needs checking. A business inquiry can describe the desired workflow without attaching a completed client record. Documentation helps a mechanic or fitter ask a better question; it does not remove the need for current physical inspection, exact component instructions or an appropriate human decision.
Practical questions
Frequently asked questions
What bike fit measurements should I record first?
Record the task, bicycle alignment and datum, then named saddle and cockpit points with units, method and repeated readings. Leave unavailable values Not measured. This is a setup record, not a prescription.
Is saddle height the distance from the floor?
Not in a BB-relative record. A floor reading needs its origin and endpoint stated; a direct BB-to-saddle length and vertical saddle Y are also different quantities.
Can I complete this without a camera or account?
Yes. Read this guide and the blank worksheet without a camera, account or local bike record. Using an interactive tool later keeps its existing consent and explicit-save boundaries.