Y-Balance Test Calculator
Balance

Y-Balance Test Calculator

Lower Quarter (YBT-LQ) — dynamic balance, reach & symmetry

Measure from the bony bump at the front of the hip (anterior superior iliac spine) to the inner ankle bone (medial malleolus). One measurement is used to normalize both legs.

Left Leg (stance)

Right Leg (stance)

Each leg is the stance leg: you balance on it and reach as far as possible with the other foot in each direction. Take six practice trials per direction on each leg first — scores climb as you learn the movement — then record the best of three scored trials.
Reaching to your limit on one leg means you will sometimes lose it. Test barefoot on a non-slip surface with something stable within grabbing distance, and stop if you feel any pain in the standing leg.
Left Composite
reference ≥94%
Right Composite
reference ≥94%
Anterior Asymmetry
How to Perform It

Three Reaches From One Spot

You stand on one leg at the center of a Y and reach as far as you can with the other foot along each of its three lines, touching lightly and returning under control. Then you switch legs and repeat.

The Layout

Seen from above, standing on the left leg and facing the top of the diagram.

Y-Balance Test layout, seen from above Three lines meet at a center point where the left foot stands. The anterior line runs straight forward. The posteromedial line runs backward and to the right, and the posterolateral line runs backward and to the left, each 135 degrees from the anterior line and 90 degrees from each other. Anterior forward Posteromedial back, toward the body’s midline Posterolateral back and across behind Stance foot (left) 135°
Directions are named relative to the standing leg, not the room. On the right leg the two rear lines swap names: posteromedial goes back to the left and posterolateral back to the right. Measure each reach from the center point to where the tip of your reaching foot touched.

The Three Reaches

Shown on the left leg. Hands stay on the hips throughout, and the reaching foot only ever touches the tape lightly — it never takes weight.

Front view illustration of the anterior reach in the Y-Balance Test: a barefoot woman with her hands on her hips balances on her left leg, its foot planted at the center of a Y of gray tape on the floor, the standing knee bent in a controlled half-squat. Her right leg reaches forward toward the viewer along the front line of the Y, the foot low and only lightly touching the tape with the toes, carrying no weight.
1 · Front view

Anterior

Sink into the standing leg and reach straight forward along the front line. Tap lightly with the toes, then return to both feet under control.

Front view illustration of the posteromedial reach in the Y-Balance Test: the same woman, hands on her hips, balances on her left leg with its foot at the center of the Y, knee bent. Her right leg reaches backward and out to her own right side along one of the two rear lines of the Y, staying on its own side without crossing behind the standing leg, the foot low and unweighted.
2 · Front view

Posteromedial

Reach backward on the reaching leg’s own side. The legs don’t cross — there’s open space between them the whole way.

Back view illustration of the posterolateral reach in the Y-Balance Test: the same woman is seen from behind with her hands on her hips, balancing on her left leg with its foot at the center of the Y, knee bent. Her right leg crosses behind the standing leg and reaches back toward her left along the other rear line of the Y, the foot low and unweighted near the end of the tape.
3 · Back view

Posterolateral

Reach backward and across, behind the standing leg, to the opposite rear line. Shown from behind because from the front the crossing leg is hidden.

Front view illustration of a common error in the Y-Balance Test: the same woman, hands on her hips, has let her reaching foot settle flat on the front line of the Y with the heel down, so her weight is shared between both feet and her torso sits between them, both knees bent as in a lunge. Supporting weight on the reaching foot makes the position far easier and inflates the reach, so the trial does not count.
Doesn’t count

Weight on the Reaching Foot

Compare with the anterior reach above. Here the reaching foot has settled flat on the tape and the weight has shifted onto it, so the reach has become a lunge on two legs. That makes it much easier to go further, which is exactly why it doesn’t count — the test measures how far you can reach while all your weight stays on one leg. If the foot lands and takes weight, repeat the trial.

Based on Plisky et al. (2006) and the standardized YBT-LQ protocol. Test barefoot, with something stable within reach. Take six practice trials in each direction on each leg before scoring, then record the best of three. A trial also doesn’t count if you lose your balance, use the reaching foot to push off the floor rather than touch it lightly, or can’t return to both feet under control — movements a still image can’t show. Keep your hands on your hips every time: free arms let you counterbalance and reach further, so changing arm position changes the score. Floor tape reproduces the layout of the commercial Y Balance kit, but the kit raises the standing foot slightly and reach distances on the two aren’t identical — use the same setup each time you retest.

Watch It Performed

Y-Balance Test — Demonstration

An external physical therapy demonstration of the three reaches on each leg.

This video is hosted externally on YouTube and is not produced by Amatal. It’s provided as a visual reference only. The demonstration may use the commercial Y Balance kit, with a raised footplate and sliding markers, rather than tape on the floor — the reaches are the same, but distances measured on the two setups aren’t identical, so stick with one. The written protocol above takes precedence if anything differs.

Related Tests
  • Single-Leg Stance — static balance on one leg, timed against age norms, where this test measures reach under control.
  • Multi-Directional Reach Test — reach in four directions from a standing position, mapping your limits of stability.
  • Functional Reach Test — forward reach without stepping, scored as a fall-risk screen rather than a symmetry check.

All Balance Tests

Disclaimer

This tool scores the Lower Quarter Y-Balance Test — how far you can reach with one foot in three directions while balancing on the other leg — and compares your two legs against published injury-risk reference thresholds. It is for general fitness and screening purposes only, not a medical assessment or a prediction of injury. Test in a clear space with something stable nearby to catch yourself, and stop if you feel unstable. If you have pain, a recent injury, or are returning to sport, consult a qualified clinician.

How the Y-Balance Test Calculator Works

The Y-Balance Test (YBT) measures dynamic balance — control of the body while it is moving, not just held still. Standing on one leg, you reach as far as you can with the other foot along three lines that form a “Y”: one forward (anterior) and two back at angles (posteromedial and posterolateral). How far you can reach while staying balanced reflects your strength, mobility, and control on the standing leg. This is the Lower Quarter version (YBT-LQ), the one used for the legs.

It grew out of the Star Excursion Balance TestAn older multi-direction reach test (the SEBT) that the YBT standardized and simplified into three directions with a fixed measuring device, improving its consistency between testers., and unlike the static balance tests on this site — where you simply hold a position — the YBT is built around comparing your two legs and flagging meaningful side-to-side differences.

Step 1: Measure Your Limb Length

Reach distances mean little on their own — a taller person reaches further simply because their legs are longer. To compare fairly, every reach is expressed as a percentage of limb lengthMeasured from the anterior superior iliac spine (the bony bump at the front of the hip) to the medial malleolus (the inner ankle bone), while lying down.. You measure once, from the front hip bone to the inner ankle bone, and the calculator uses it to normalize both legs.

Step 2: Reach in Three Directions

  • Balance on one leg — the stance leg, the one being tested — with your foot at the center.
  • Reach as far as you can with the free foot along each line (anterior, then posteromedial, then posterolateral), lightly pushing the reach marker without resting weight on it, then return to a controlled two-foot stance.
  • A reach doesn’t count if you lose balance, put weight on the reaching foot, push the marker rather than touch it, or can’t return under control.
  • Practice first: the standard protocol uses six practice trials in each direction, on each leg, before anything is scored. Reach scores climb over the first attempts as you learn the movement, so skipping this understates your result.
  • Then take the best of three good scored trials in each direction, for each leg.

Step 3: Normalize and Score

Each reach is converted to a percentage of limb length:

Normalized reach = (reach ÷ limb length) × 100

The three directions are then combined into a single composite scoreOne number summarising overall reach for a leg, normalized to limb length so it can be compared between people and against reference thresholds. for each leg:

Composite = [(Anterior + Posteromedial + Posterolateral) ÷ (3 × limb length)] × 100

Step 4: Compare Left to Right

The most useful signal the YBT gives is not how far you reached, but how evenly your two legs perform. The headline number is your anterior asymmetry — the raw difference between your left and right forward reaches:

Anterior asymmetry = | Right anterior reach − Left anterior reach |

This is kept in real distance (centimeters or inches), not a percentage, because the best-known injury-risk threshold is defined in centimeters. The calculator also reports the composite difference between legs, in percentage points.

Reading the Reference Thresholds

The calculator checks your result against two widely cited thresholds and marks each as within reference or above / below reference:

  • Anterior asymmetry of 4 cm or more — a left/right forward-reach gap this large has been linked to higher lower-limb injury risk.
  • Composite below 94% of limb length — a low overall reach score has been linked to higher injury risk. Note that in the original study this finding was established in the girls; the anterior-asymmetry threshold applied to the players overall.

Both come from Plisky and colleagues’ 2006 study of high-school basketball players, where girls below the 94% composite were 6.5 times more likely to be injured and players of either sex with more than 4 cm of anterior asymmetry were 2.5 times more likely. That origin matters: these numbers are the common default, not a universal standard. In collegiate American football, for instance, a lower composite cut-off (around 89.6%) fit better, and the anterior-asymmetry threshold didn’t predict injury at all. Reviews of the test are explicit that the right cut points depend on age, sex, and sport. The calculator therefore presents these as reference flags, not a verdict.

Why Asymmetry Leads, and Why There Are No Tiers

You’ll notice this calculator does not sort you into “poor” to “excellent” bands the way a percentile-based test would. That is deliberate, and it comes down to honesty about the data:

  • There is no single population norm. Reach scores differ markedly by sport, sex, age, and even country, and the published reference datasets cover specific groups (basketball players, soldiers, particular sports) rather than people in general. Inventing a universal tier scale would imply a precision the evidence doesn’t support.
  • Asymmetry is a fairer signal. Comparing your two legs to each other sidesteps the question of which population’s norm applies to you — your own opposite leg is the most relevant comparison there is. That is why the left/right difference is the headline, and the composite is shown as an honest number against a clearly-labeled reference line.

The Reach Profile and Breakdown

  • Reach Profile (radar) — plots normalized reach in all three directions for both legs. The shape is normally lopsided — a short anterior reach with longer posterior reaches — and that’s expected. Gaps between the blue (left) and purple (right) outlines show your asymmetry at a glance.
  • Reach Breakdown (table) — the raw reach, the normalized percentage, and the left/right difference for each direction, with anterior highlighted and the composite on the bottom row.

A Note on Limb Length

The standard protocol measures limb length on each leg separately. This calculator asks for one measurement and applies it to both, which keeps the form simple and is close enough for most people — but if your legs differ noticeably in length, both composite percentages will be shifted slightly, and comparing them to each other becomes less exact. The anterior-asymmetry check is unaffected either way, because it compares raw reach distances and never divides by limb length.

What Affects Your Score

  • Technique and protocol details — Whether the hands stay on the hips or move freely, and whether the stance heel is allowed to lift, both change reach scores enough to move some people across a threshold. Keep your method consistent if you want to compare over time.
  • Mobility and strength — Ankle, hip, and trunk mobility and the strength of the hip and thigh muscles all feed into how far you can reach with control.
  • Warm-up, footwear, and fatigue — Reaches are typically done barefoot after a warm-up; tiredness and surface affect control.
  • Practice — Scores improve over the first few attempts as you learn the movement, which is why practice trials precede the scored ones.

Data Sources

  • Plisky PJ, et al. (2006). Star Excursion Balance Test as a predictor of lower extremity injury in high-school basketball players — origin of both reference thresholds: anterior asymmetry greater than 4 cm (2.5× injury risk, players overall) and composite below 94% of limb length (6.5×, established in the girls).
  • Butler RJ, et al. (2013). Collegiate American football — found a lower composite cut-off (~89.6%) and no predictive value for anterior asymmetry, illustrating how cut points shift by population.
  • Plisky PJ, et al. (2021). Systematic review and meta-analysis of the YBT-LQ — confirms good reliability and that predictive cut points vary by age, sex, and sport.
  • Protocol & measurement — limb length measured from the anterior superior iliac spine to the medial malleolus, the standard YBT-LQ method.

Limitations and Important Caveats

This calculator turns reach measurements into a symmetry and reference-threshold screen. It cannot do more than that:

  • It is a screen, not a prediction. Meeting the thresholds lowers the odds of injury in the studied groups; it does not guarantee safety, and being flagged does not mean injury is coming.
  • The thresholds are population-specific. The 4 cm / 94% defaults fit high-school basketball; your sport, age, and sex may warrant different numbers, and clinicians usually combine the YBT with other tests rather than relying on it alone.
  • Measurement quality matters. Inconsistent technique, an unmarked or improvised reach setup, or a rough limb-length measurement all reduce accuracy. Results are most meaningful when the method is standardized and repeated.
  • It reflects one session. A single test is a snapshot; a trend across sessions, especially through rehab or training, is more informative.

Disclaimer:
This calculator scores the Lower Quarter Y-Balance Test against published injury-risk reference thresholds. It is for general informational and fitness-screening purposes only and is not a medical assessment, a diagnosis, or a prediction of injury. Always test in a safe space with stable support within reach, and stop if you feel unstable or experience pain. The reference thresholds are drawn from specific athletic populations and may not apply to you; a result on this test should not, on its own, drive decisions about training or returning to sport. If you have pain, a current or recent injury, or are rehabilitating one, consult a qualified healthcare or sports-medicine professional. This tool does not replace professional assessment.