What is a clinically significant leg length discrepancy?

Most clinicians consider discrepancies under 10 mm (about 3/8 inch) mild and often asymptomatic. Discrepancies of 10–20 mm are moderate and may warrant a heel lift. Over 20 mm is typically considered significant and may require orthopaedic evaluation.

What is the heel lift recommendation based on?

A common guideline is to prescribe a lift equal to roughly 50–75% of the discrepancy, introduced gradually. This tool shows 60% as a starting estimate. Always confirm with a qualified clinician before using an orthotic.

What is the difference between direct and indirect measurement?

Direct measurement uses a tape from the anterior superior iliac spine (ASIS) to the medial malleolus. Indirect (block) measurement involves placing calibrated blocks under the short side until the pelvis levels, then reading the block height.

Can leg length discrepancy cause back pain?

Yes. Even moderate LLD can contribute to pelvic tilt, scoliosis-like posture, and chronic low back or hip pain. Correction with a heel lift or orthopaedic shoe modification often helps, but diagnosis should come from a professional.

Is this calculator a medical diagnosis?

No. This tool provides an educational estimate only. For a clinical diagnosis and treatment plan, consult a physiotherapist, orthopaedic surgeon, or sports medicine physician.

Leg Length Discrepancy Calculator

Enter both leg measurements to instantly find the discrepancy and the typical heel lift recommendation.

Enter Measurements

Measure both legs using the same method and unit.

Unit

Centimeters (cm) Inches (in)

Measurement Method

Left Leg (cm)

Right Leg (cm)

Results

Enter measurements and click Calculate.

Summary

Leg length discrepancy (LLD) occurs when one leg is measurably shorter than the other, causing gait asymmetry, pelvic tilt, and sometimes chronic pain. This calculator accepts direct tape-measure values or indirect block-method heights and computes the discrepancy in your chosen unit. It then provides a standard heel-lift starting estimate (60% of the discrepancy) along with an interpretation guide ranging from negligible to significant.

How it works

Select your preferred unit (cm or inches).
Choose the measurement method: direct tape measure or indirect block method.
Enter the measured length for each leg.
The calculator shows the discrepancy, which leg is shorter, and a heel lift guideline.
Review the interpretation notes to understand clinical significance.

Use cases

Pre-screening before visiting an orthopaedic specialist.
Estimating heel lift height for shoe inserts.
Tracking leg length changes during growth or post-surgery.
Evaluating posture asymmetry related to limb length inequality.
Physical therapy baseline documentation.
Sports medicine functional assessment.

Frequently Asked Questions

Last updated: 2026-06-19 · Reviewed by Nham Vu