Mobility
Flexibility Score Calculator
Rate your sit-and-reach score against the Canadian (CPAFLA) norms for your age and sex, with an approximate percentile and how far you are from Very good.
Result
4 cm past your toes. Around the middle for your age. Stretching most days improves reach over several weeks; retest the same way each month.
Where you sit in your age group
The CPAFLA categories, each about a fifth of people your age and sex.
How to use it
- Do the sit-and-reach on the CPAFLA box scale: feet flat against the box at the 26 cm (about 10¼ in) mark, legs straight, reach forward slowly with both hands and take the best of two. With a ruler at home, add 26 cm to how far past your toes you reach, or subtract if you fall short. Test at the same time of day after the same brief warm-up each time.
- Enter the score, your age and sex. The rating comes from the CPAFLA norms for your age group and sex, so a 45-year-old rated Good is doing as well for their age as a 20-year-old rated Good.
- Below-average scores for your age point to tight hamstrings or lower back; on their own they say little about pain or injury risk.
- Evidence-based flexibility improvement: 30-second static stretches, 4+ times per week, produces measurable range-of-motion gains within 4–8 weeks. Dynamic warm-up before training is more effective than static stretching for pre-workout preparation.
- Range gained from stretching fades when you stop, so keep 1–2 flexibility sessions a week to hold it.
Questions people usually ask
What is a sit-and-reach test?
A sit-and-reach test measures hamstring and lower-back flexibility. You sit with legs straight and feet against a box and reach forward as far as possible. On the CPAFLA box scale this tool uses, the feet sit at the 26 cm mark, so the score is 26 plus how far past your toes you reach.
Why can my score be negative?
On the box scale it is not: falling short of your toes gives a score below 26 cm, not below zero. If you measure from your toes with a ruler, a negative number just means you fell short; add 26 to it to get the box score, so 8 cm short scores 18.
How accurate is this flexibility assessment?
The ratings use the Canadian (CPAFLA, CSEP 2003) sit-and-reach norms by age and sex, and the percentile is interpolated within those categories, so it is an approximation. Warm-up, technique and body proportions move a score by a few centimetres.
How long does it take to improve flexibility?
Regular stretching improves range of motion within weeks for most people; how much depends on how often and how long you stretch, so consistency matters more than any single session. Re-test under the same warm-up to compare fairly.
Is this tool free and private?
Yes. AI Fit Hub tools are free, browser-based, and no-signup. Your inputs stay in your browser.
Does this replace medical or fitness assessment?
No. This is a general estimate based on population norms — not a medical assessment. Consult a physiotherapist for a full flexibility evaluation.
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Background on the Flexibility Score Calculator
- Guide How to Stretch Properly: Checklist, Dynamic vs Static
How to stretch properly: dynamic moves before training, static holds of about 30 seconds after or on rest days, 60 seconds per muscle, 2-3 days a week.
- Statistics Flexibility Statistics: Norms, Methods & Effects
Flexibility statistics: range-of-motion norms, stretching methods compared, changes with age and links to injury, each figure with its source.
- Statistics Mobility & Injury Statistics: Risk Factors and Outcomes
Mobility and injury statistics: how common injuries are, risk factors, what interventions achieve and recovery times, each figure with its source.
Articles
- 4 min read How to Stretch Lower Back Safely: 5 Physio-Backed Moves
Stretch your lower back with knee-to-chest, pelvic tilts and heel slides from the UK physio body, plus NHS advice on staying active and red-flag symptoms.
Use it from an agent or code
Any agent can run this calculator by URL: put the inputs in the query string and get JSON back, with the inputs that used defaults and a line to cite (add format=md for markdown). MCP clients reach it through https://aifithub.io/mcp.
https://aifithub.io/api/run/flexibility-score-calculator?reach_cm=30&age=30&sex=male
In code, import the same module; it runs where you import it, with no request or key.
import { compute } from "https://aifithub.io/engines/flexibility-score-calculator.js";Input and output contract, TypeScript types and the guide for agents.