Purpose: Regarding the high prevalence of low back pain in various communities and the need to determine an appropriate treatment plan for these patients, examining their functional limitation and disability level is of utmost importance. In this regard, one of the important indicators is Lumbar range of motion. Measurement of the range of motion is a common and appropriate method for determining the functional limitation of the spine and also to examine the effectiveness of various therapeutic interventions. This study was conducted with the purpose of examining the reliability of measuring lumbar range of motion using bubble inclinometer and tape measure. Methods:This methodological study was performed on 20 healthy males (29-52 years old) and 13 male patients with chronic non-specific low back pain (30-58 years old) in 2015. The ranges of lumbar forward and backward and side bending were measured with bubble inclinometer and rotation with tape measure for both groups. Two measurements were conducted in one day with an interval of one hour to examine the within day reliability, and a third measurement was conducted one week later to examine the between days reliability. Statistical inference was made through calculation of intraclass correlation coefficients (ICC) and standard error of measurement (SEM). All data analysis was done by SPSS version 18. Results:The ICC and SEM values related to the within days and between days reliability were acceptable. The within day and between days ICC range were 0.770-0.982 and 0.835-0.977, respectively. SEM range was 0.38-1.20. However, the results of the reliability values of between days measuring of extension in prone position, by using bubble inclinometer, in patients with slight low back pain were low (ICC=0.177 and SEM=5.35). Conclusion:Results of the present study showed that measuring the lumbar range of motion with bubble inclinometer and tape measure (except measuring extension in prone position by using bubble inclinometer in patients with low back pain) was highly reliable. Therefore, these 2 non-invasive and reliable tools can be used to measure the lumbar range of motion and also to follow-up the effectiveness of therapeutic interventions.