The drop jump, also called the depth jump or box jump, is a fitness test of leg strength and power which requires the athlete to "drop off" a box and immediately jump as high as they can. There is also an Incremental Drop Jump test used for measuring reactive leg strength, where the athlete jumps after dropping from a series of different heights. There is also a drop jump assessment as part of the Bosco Ergo Jump System. See about other vertical jump tests.

How to Use This Calculator

Follow these steps to calculate your drop jump test results and Reactive Strength Index:

  1. Enter Flight Time - Input the time (in seconds) that you were airborne during the jump. This is measured from the moment your feet leave the ground until they contact it again. Typical values range from 0.35 to 0.65 seconds.
  2. Enter Ground Contact Time - Input the time (in seconds) your feet were in contact with the ground between landing from the drop and taking off for the jump. Elite athletes aim for contact times under 0.180 seconds.
  3. Enter Box Height (Optional) - Record the height of the box you dropped from for reference. Common heights are 30cm, 40cm, 50cm, and 60cm.
  4. Click Calculate - The calculator will instantly compute your jump height and RSI score with performance classification.

Pro Tip: For accurate results, ensure your timing equipment is properly calibrated. Contact mats and force platforms provide the most reliable measurements for drop jump testing.

What is the Drop Jump Test?

Purpose: To measure the explosive force of the lower limbs and reactive strength capabilities.

Equipment required: vertical jump measurement mat (e.g. just jump mat, Myotest, infrared laser system), boxes of various heights.

Pre-test: Explain the test procedures to the subject. Perform screening of health risks and obtain informed consent. Prepare forms and record basic information such as age, height, body weight, gender, test conditions. Check and calibrate timing mat measurement. Subject to perform an appropriate warm-up. See more details of pre-test procedures.

drop jump test technique showing athlete dropping from box and jumping

Procedure: This test is performed from a pre-set box height. The heights used can be between 20 cm and 100 cm. The athlete stands on the box, adjacent to the timing mat. Hands are placed on the hips, and stay there throughout the test. The athlete then drops down off the box onto the mat, bending the knees on landing, then immediately performs a maximal vertical jump. The athlete jumps vertically as high as possible, and lands back on the mat with both feet landing at the same time, returning to the takeoff spot. Several trials can be performed, with adequate rest between trials.

The Science Behind the Calculation

This calculator uses two primary formulas to analyze your drop jump performance:

Jump Height Formula

Jump Height = 4.9 × (0.5 × Flight Time)²

Where:

  • 4.9 = Half of gravitational acceleration (9.8 m/s² ÷ 2)
  • Flight Time = Time in seconds from takeoff to landing
  • Result is in meters (multiply by 100 for centimeters)

Reactive Strength Index (RSI) Formula

RSI = Jump Height (m) ÷ Ground Contact Time (s)

Where:

  • Jump Height = Calculated from flight time in meters
  • Ground Contact Time = Time feet are on ground in seconds
  • Higher RSI indicates better reactive strength

Scoring: Depending on the equipment, there may be measurements of contact time, flight time, height of the jump, power of the jump, and ground reaction forces. The jump height time is the time between the participant's feet leaving the timing mat or force platform and when they contacted it again. Ground contact time is the time between the first foot contact with the force platform and when the participant's feet left the mat. Reactive strength index (RSI) can be calculated by dividing the jump height by the ground contact time.

Understanding Your RSI Results

Reactive Strength Index values vary based on sport, training background, and testing protocols. The following classifications provide general guidelines:

RSI Score Classification Typical Population
> 3.0 Elite Professional sprinters, jumpers
2.5 - 3.0 Excellent Competitive athletes, power sports
2.0 - 2.49 Good Trained athletes, team sports players
1.5 - 1.99 Average Recreational athletes, fitness enthusiasts
1.0 - 1.49 Below Average Beginners, untrained individuals
< 1.0 Needs Improvement May indicate strength or technique issues

Sport-Specific Applications

The drop jump test and RSI measurement are particularly valuable for athletes in sports requiring rapid force development:

Track & Field Athletes

Sprinters and jumpers benefit most from high RSI scores. Elite long jumpers and sprinters typically achieve RSI values above 3.0, reflecting their exceptional ability to convert ground contact into explosive propulsion.

Team Sports (Basketball, Volleyball, Football)

Players requiring repeated explosive movements should target RSI values between 2.0-2.5. The drop jump test helps identify athletes who can maintain power output during game situations.

Combat Sports

Wrestlers, judokas, and MMA fighters use reactive strength for explosive takedowns and rapid direction changes. RSI testing helps optimize plyometric training programs for these athletes.

Endurance Athletes

While not the primary focus, distance runners can benefit from moderate RSI levels (1.5-2.0) to improve running economy and reduce ground contact time during each stride.

⚠️ Important: This test requires athletes with a good degree of leg strength, as the forces through the body are much higher than for a standard vertical jump test. This test can also be used to assess ACL injury risk.

How to Improve Your Drop Jump Performance

Based on your RSI results, consider these training approaches:

If RSI is Below 1.5 (Focus on Strength)

  • Build foundational leg strength with squats and deadlifts
  • Practice basic jumping mechanics without the drop component
  • Perform landing drills to improve force absorption
  • Consider starting with lower box heights (20-30cm)

If RSI is 1.5-2.0 (Focus on Rate of Force Development)

  • Incorporate contrast training (heavy squats followed by jumps)
  • Practice depth jumps at moderate heights (30-40cm)
  • Add single-leg plyometrics to address imbalances
  • Focus on minimizing ground contact time

If RSI is Above 2.0 (Focus on Sport-Specific Transfer)

  • Vary drop heights to find optimal performance zone
  • Include multi-directional plyometrics
  • Progress to advanced bounding and hurdle jumps
  • Monitor fatigue and recovery to prevent overtraining

Test Considerations

Disadvantages:

  • The standard size boxes are not readily available, and may even need to be custom made.
  • Results can be easily influenced by body position during take-off and landing. If an athlete bends their legs when landing the flight time and therefore jump height calculation can be affected.

Notes:

  • This test requires athletes with good degree of leg strength, as the forces through the body are much higher than for a standard vertical jump test.
  • This test can be used to assess ACL injury risk.
  • Make sure the participants do not jump off the box, rather than simply 'stepping-off'.
  • No arm-swinging is allowed.

Frequently Asked Questions

What is a good Reactive Strength Index (RSI)?

A good RSI score depends on your sport and training level. For general athletic populations, an RSI of 2.0 or above is considered good. Elite sprinters and jumpers often achieve RSI values above 3.0, while recreational athletes typically score between 1.0-1.5. Your optimal RSI target should be based on your specific sport demands.

What box height should I use for the drop jump test?

Start with a height that allows you to maintain proper form and quick ground contact. Beginners should use 20-30cm, intermediate athletes 40cm, and advanced athletes 50-60cm. The optimal height produces the highest RSI score—too high and contact time increases; too low and jump height decreases.

How is jump height calculated from flight time?

Jump height is calculated using the physics formula: Height = 4.9 × (0.5 × Flight Time)². This derives from the free-fall equation, where 4.9 m/s² represents half the gravitational acceleration. For example, a 0.5 second flight time equals approximately 30.6 cm jump height.

How often should I test my drop jump performance?

For monitoring training adaptations, test every 4-6 weeks. During competition preparation, monthly testing helps track readiness. Some coaches use RSI as a daily readiness indicator, though this requires consistent testing conditions and shouldn't replace subjective wellness monitoring.

What's the difference between drop jump and countermovement jump tests?

The drop jump measures reactive strength (ability to quickly reverse direction after landing), while the countermovement jump measures general leg power from a stationary position. Drop jumps involve higher ground reaction forces and emphasize the stretch-shortening cycle more than countermovement jumps.

Can drop jump testing predict injury risk?

Research suggests asymmetries in drop jump performance between legs may indicate increased ACL injury risk. Athletes with significantly different contact times or RSI values between limbs should address these imbalances through targeted training before progressing plyometric intensity.

Should I use arms during the drop jump test?

Standard protocols require hands on hips throughout the test to isolate leg power. However, sport-specific testing may allow arm swing to better replicate game situations. Whatever protocol you choose, maintain consistency across all testing sessions for valid comparisons.

Similar Tests

Related Pages

Reactive Strength Index

Understanding the ratio between jump height and ground contact time.

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Vertical Jump Equipment

Discussion about various vertical jump measurement systems available.

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Vertical Jump Techniques

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Anaerobic Tests

See the complete list of anaerobic tests for leg strength and power.

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References

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  3. Schmidtbleicher, D. (1992). "Training for power events." In P.V. Komi (Ed.), Strength and Power in Sport (pp. 381-395). Blackwell Scientific.
  4. Bosco, C., & Komi, P.V. (1979). "Potentiation of the mechanical behavior of the human skeletal muscle through prestretching." Acta Physiologica Scandinavica, 106(4), 467-472.
  5. Byrne, P.J., Moran, K., Rankin, P., & Kinsella, S. (2010). "A comparison of methods used to identify 'optimal' drop height for early phase adaptations in depth jump training." Journal of Strength and Conditioning Research, 24(8), 2050-2055.
  6. McClymont, D. (2003). "Use of the reactive strength index (RSI) as an indicator of plyometric training conditions." Science and Football V, 408-416.
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