How This Calculator Works

This calculator measures your hip-flexion range of motion using the Active Straight Leg Raise (ASLR) — a widely used screen of how far each straight leg lifts away from the floor, reflecting hamstring extensibility and the ability to move one leg freely without the pelvis or opposite leg compensating. You enter the angle each leg reaches, and the calculator scores both sides separately, classifies each into a five-tier category, flags any side-to-side asymmetry, and computes your Flexibility Age and an estimated percentile for your age and sex.

Step 1: Enter Your Details

The calculator needs four inputs: your sex, your age, and the angle reached by your left and right legs.

• SexHip-flexion mobility norms are reported separately for men and women, who differ on average in pelvic structure and soft-tissue flexibility — women tend to reach slightly higher at every age. — selects which normative table you are compared against.
• Age — determines the mobility standards expected for your stage of life.
• Left & Right angleEach leg is scored on its own. Measuring both is what lets the tool flag a meaningful left-versus-right gap rather than just an overall number. — the angle each straight leg reaches from the floor, entered in degrees. 0° means the leg is flat on the floor; 90° means it points straight up at the ceiling.

The Test Protocol

For results that match the norms, the test must be performed the standard way — lying flat with the opposite leg controlled:

• Setup: Lie on your back on a firm, flat surface. Legs straight, arms relaxed at your sides, head down, toes pointing toward the ceiling.
• Keep the down leg flat:The back of the resting knee should stay in contact with the floor. Once it lifts or the pelvis rolls, the test is over — that point marks your true active range, not how high you could swing the leg with momentum. Press the non-moving leg into the floor and keep its knee straight throughout.
• Raise slowly: Lift one leg as high as you can while keeping that knee fully straight and the toes pointing up. Move under control — no kicking, swinging, or bouncing.
• Read the angle: Record the angle the moving leg makes with the floor at the highest point you reach before the knee bends, the opposite leg lifts, or the pelvis rotates. Use a goniometer or a phone angle/level app for accuracy. Repeat for the other leg, and record each side separately.

How Your Category Is Determined

Each leg's angle is compared against the minimum required for each tier at your age and sex, and that leg is placed in the highest tier it qualifies for. To keep every assessment on this platform consistent, the same five-tier scale used across the site applies here:

• Low — below the typical range for your group. Limited hip-flexion mobility, often tight hamstrings or guarding. The most to gain from regular mobility work.
• Intermediate — around the population average. Typical of recreationally active adults who do not stretch regularly.
• Advanced — above average for your group. Reflects decent habitual mobility or some consistent stretching practice.
• Superior — well above average. Characteristic of people who train mobility consistently or do flexibility-focused activity.
• Elite — top tier for your age and sex. Among the most mobile performers in the demographic.

Each leg also shows an approximate FMS-equivalent scoreThe Functional Movement Screen scores the ASLR 1–3 by where the moving ankle lines up against landmarks on the down leg, not by a measured angle — so this is an approximate translation, not the exact FMS criteria. (out of 3), mapped from the angle as a rough bridge to the FMS version of the test:

Side-to-Side Symmetry

Because both legs are scored separately, the calculator reports the difference between them and tells you which side is tighter. Symmetry matters as much as raw range — a large imbalance can point to a one-sided restriction worth addressing:

• Under 5° — well balanced; treated as effectively equal.
• 5° to 14° — a mild difference, within the range seen in many healthy people.
• 15° or moreThe 15° threshold is a practical flag for "worth a closer look," not a medical diagnosis. Persistent or painful asymmetry is best assessed by a qualified professional. — flagged as a notable asymmetry, with the tighter side identified for targeted mobility work.

The Smooth Age Model

Hip-flexion mobility declines gradually and continuously with age — not in sudden steps. To reflect this, the calculator anchorsRepresentative values are placed at ages 18, 25, 35, 45, 55, and 65, and the tool reads off a smooth value for every age in between. the tier standards at six representative ages — 18, 25, 35, 45, 55, and 65 — then interpolates a smooth value for every age in between:

Ages below 18 are held at the youngest values, and ages beyond 65 are extrapolated by continuing the downward trend out to 75. The result is the smooth band chart and the per-five-year standards table. Values shown between the anchor ages — and all values below 18 or above 65 — are modeled estimates.

How to Read the Standards Table

The standards table lists one row for every five years of age and one column for each of the five levels. The header labels are color-coded to match the chart bands — on a phone the headers shorten to single letters (L · I · A · S · E); tap any header to see its full name. Every value is shown in degrees.

• Each cell is a single number — the minimum. It shows the smallest angle needed to enter that level at that age. If a leg reaches or exceeds it, that leg has reached that level.
• The Low column is the exception.Low has no real minimum — it runs from the bottom of the scale up to the Intermediate threshold. The number shown is just a representative point inside that range. Because Low spans from the bottom up to the Intermediate cutoff, the number shown there is a representative value for display only, not a threshold you need to hit.
• Your row and level are highlighted. The row closest to your age is shaded, and the cell for your overall level (based on both legs combined) is filled with that tier's color.

Flexibility Age

Your Flexibility AgeThe age at which your mobility would be considered typical (mid-range) performance. Conceptually similar to the "fitness age" used in cardiovascular testing. is the age at which your result would be average. It is calculated from the average of your two legs: if your combined mobility is greater than typical for your actual age, your Flexibility Age is younger; if less, it is older.

The calculator scans the smooth age model to find the age whose median angle matches your average, giving an intuitive single-number summary of where your hip mobility sits on the aging curve.

Percentile Estimate

The percentile estimates the share of people in your age-and-sex group who are less mobile than you, based on your two-leg average. Because the norms are expressed as tier boundaries rather than a full distribution, the percentile is approximated by mapping each tier threshold to its corresponding percentile and interpolating between them:

Your average angle is placed along this scale to produce an approximate percentile. It is a reasonable guide, not a precise population statistic.

How Age and Sex Change Your Score

Both inputs change the numbers your result is measured against:

• Age changes the thresholds. The calculator recomputes the angle requirement for every tier at your exact age. Because mobility standards decline with age, the same angle is judged against lower requirements as you get older — so an identical raise can place you in a higher tier at 55 than it would at 25. This is why the standards table and chart drift downward from left to right.
• Sex selects a different table. Choosing male or female swaps in a separate set of normative values. Women's thresholds sit higher at every age, so the same angle is scored against different benchmarks depending on which table applies.

Why Hip Mobility Matters

The ASLR is about more than touching your toes. Adequate hip-flexion range underpins everyday movements like bending, lifting, and climbing stairs, and athletic patterns like sprinting, hinging, and squatting to depth. Restricted hamstring extensibility is one factor commonly associated with altered movement mechanics, and the test's emphasis on keeping the opposite leg flat also reflects core and pelvic control — the ability to move one limb without the rest of the body compensating.

Important context: a single mobility number does not predict injury on its own, and "more" is not always "better" — very high range without control is its own consideration. Treat the ASLR as one general indicator among several, useful for tracking your own progress over time and for spotting a side-to-side gap, rather than a standalone verdict on your health.

Data Sources and Methodology

The test procedure and the structure of the norms draw on established movement-screening and range-of-motion references:

• Cook, G., Burton, L., & Hoogenboom, B. (2006). Pre-participation screening: the use of fundamental movements as an assessment of function. North American Journal of Sports Physical Therapy — the Functional Movement Screen, which includes the ASLR and its 1–3 scoring.
• American Academy of Orthopaedic Surgeons (AAOS) and the AMA Guides to the Evaluation of Permanent Impairment — standard reference values for normal hip-flexion range of motion.
• Research on hip range of motion and age — studies consistently show active hip-flexion range declines gradually across adulthood, which informs the downward slope of the age model used here.
• ACSM's Guidelines for Exercise Testing and Prescription (11th Edition, 2021). Wolters Kluwer — standardized flexibility-testing principles and interpretation.

A note on the tier values: unlike a test such as the sit-and-reach, the ASLR does not have a single, universally published set of five-tier degree norms by age and sex. The thresholds in this calculator are representative values, calibrated against the published ranges of normal active hip-flexion range of motion and structured to stay consistent with the other assessments on this platform. They are a sensible, transparent benchmark for self-comparison and progress tracking — not figures lifted verbatim from one normative table.

Limitations and Important Caveats

This calculator provides an estimate, not a clinical measurement. Several factors affect how precisely it reflects your true mobility:

• Representative, modeled norms. The tier thresholds are representative values rather than a single published table, and per-age numbers between the anchors — plus values below 18 or above 65 — are interpolated or extrapolated.
• Approximate percentile and FMS score. The percentile is mapped from tier boundaries rather than a full population distribution, and the FMS-equivalent is a rough angle-based translation, not the official FMS landmark criteria.
• Measurement accuracy.Eyeballing the angle, letting the knee bend slightly, or allowing the down leg to lift all change the reading. A goniometer or angle app and a consistent stopping point make retests comparable. Self-measured angles are sensitive to technique. Small differences in how the knee, pelvis, and opposite leg are controlled can shift the number noticeably.
• What the test measures. The ASLR blends hamstring extensibility, hip mobility, and trunk/pelvic control. It is a useful general indicator, not an isolated measure of any single tissue.
• Warm-up has a large effect. Mobility scores rise when muscles are warm. A cold test reads lower than a warm one, so warm up first and stay consistent between retests.
• Single-test snapshot. Time of day, recent activity, and warm-up all affect a single test. For tracking progress, retest under the same conditions every few weeks.

Disclaimer:
This calculator provides an estimate based on representative normative ranges and a modeled age curve. Real mobility depends on training history, body proportions, warm-up, time of day, and individual variation. Always warm up before any mobility test and raise the leg slowly — never bounce or force the movement — and stop immediately if you experience pain, sharp pulling, or numbness or tingling down the leg. This tool is for general informational purposes only and should not be considered medical, fitness, or training advice. Consult a healthcare provider before beginning a new exercise program, especially if you have a pre-existing back, hip, or nerve condition, are over the age of 45, or have been sedentary for an extended period.