Use this Free Fall Calculator to find time, distance fallen, final velocity, and average speed for ideal vertical motion under gravity. It works from either a known height or a known time and supports gravity presets for Earth, Moon, Mars, Jupiter, or a custom gravity value.

Reviewed by: AjaxCalculators Editorial Team
Last updated: May 2, 2026
Method source: Standard one-dimensional kinematics for free fall with constant gravitational acceleration and no air resistance
Editorial standards: AjaxCalculators Editorial Policy

What This Free Fall Calculator Calculates

This calculator estimates the main results of ideal vertical free-fall motion using constant acceleration. Depending on the mode selected, it can calculate:

• Time: how long the object is falling or moving vertically
• Distance fallen: vertical displacement covered during the motion
• Final velocity or final speed: how fast the object is moving at the end of the interval
• Average speed: the overall rate of motion across the selected interval

It supports two common calculation modes:

• From height: enter vertical displacement to estimate time and impact speed
• From time: enter elapsed time to estimate distance and final speed

This makes the calculator useful for physics homework, basic kinematics practice, gravity comparisons, fall-time estimates, and learning how initial upward or downward velocity changes vertical motion.

What Free Fall Means

Free fall means motion under the influence of gravity alone. In the ideal textbook model, air resistance is ignored and gravity is treated as constant.

That ideal model is useful because it lets you use the standard constant-acceleration equations. Near Earth’s surface, a common standard gravity value is:

g = 9.80665 m/s²

In real life, falling objects can be affected by air resistance, shape, size, wind, spin, and altitude. This calculator uses the simpler ideal model so the motion can be solved with standard kinematics.

How the Free Fall Calculator Works

This calculator uses the standard constant-acceleration equations for one-dimensional vertical motion.

With downward treated as positive, the main equations are:

s = v₀t + ½gt²

v = v₀ + gt

In these equations:

• s = vertical displacement
• v₀ = initial vertical velocity
• v = final vertical velocity
• g = gravitational acceleration
• t = elapsed time

In From time mode, the calculator uses the entered time directly to find distance and final velocity.

In From height mode, the calculator solves the displacement equation for time, then uses that time to calculate final velocity.

Formula Summary

What You Want to Find	Formula	Known Values Needed
Distance from time	s = v0t + ½gt²	Initial velocity, gravity, and time
Final velocity from time	v = v0 + gt	Initial velocity, gravity, and time
Final velocity from displacement	v² = v0² + 2gs	Initial velocity, gravity, and displacement
Time from height	t = (-v0 + √(v0² + 2gs)) / g	Initial velocity, gravity, and vertical displacement
Distance from rest	s = ½gt²	Gravity and time, when v0 = 0
Speed from rest	v = gt	Gravity and time, when v0 = 0

Direction Convention: What Positive and Negative Velocity Mean

This calculator’s equations are easiest to understand when downward is treated as positive. Under that convention:

Input Sign	Meaning	Example
Positive initial velocity	Object is initially moving downward	An object thrown downward from a height
Zero initial velocity	Object is dropped from rest	A dropped ball with no initial push
Negative initial velocity	Object is initially moving upward	A ball thrown upward before falling back down

The sign tells you direction. The speed is the magnitude of velocity, so speed is usually shown as a non-negative value.

Gravity Presets and Custom Gravity

The calculator may include gravity presets so you can compare free fall under different gravitational accelerations. Lower gravity usually means longer fall time and lower final speed for the same height, while higher gravity usually means shorter fall time and higher final speed.

Gravity Setting	Approximate Meaning	Effect on Free Fall
Earth	Common near-surface gravity value	Standard classroom reference for many problems
Moon	Lower gravity than Earth	Objects fall more slowly in the ideal model
Mars	Lower gravity than Earth but higher than the Moon	Fall time is longer than Earth for the same height
Jupiter	Much stronger gravity than Earth	Objects accelerate downward faster in the ideal model
Custom gravity	User-entered value	Useful for textbook problems or special comparisons

For most near-Earth educational examples, the standard value 9.80665 m/s² is commonly used. Some textbooks may round this to 9.8 m/s² or 10 m/s² for simpler calculations.

Worked Example: Dropped from Rest from a Known Height

Suppose an object is dropped from rest from a height of 20 m on Earth.

Step 1: Identify the known values
Initial velocity, v₀ = 0 m/s
Displacement, s = 20 m
Gravity, g = 9.80665 m/s²

Step 2: Use the displacement equation
s = v₀t + ½gt²

Because the object starts from rest, v₀ = 0, so:

20 = 0.5 × 9.80665 × t²

Step 3: Solve for time
20 = 4.903325t²
t² = 20 / 4.903325 ≈ 4.0782
t ≈ 2.02 s

Step 4: Find final velocity
v = v₀ + gt
v = 0 + 9.80665 × 2.02
v ≈ 19.81 m/s

Step 5: Find average speed
Average speed = distance / time
Average speed = 20 / 2.02 ≈ 9.90 m/s

Result: An object dropped from 20 m takes about 2.02 seconds to fall and reaches a final speed of about 19.81 m/s in the ideal no-air-resistance model.

Worked Example: From Time

Suppose an object is dropped from rest and falls for 3 seconds on Earth.

Step 1: Identify the known values
Initial velocity, v₀ = 0 m/s
Time, t = 3 s
Gravity, g = 9.80665 m/s²

Step 2: Find distance fallen
s = v₀t + ½gt²
s = 0 × 3 + 0.5 × 9.80665 × 3²
s = 4.903325 × 9
s ≈ 44.13 m

Step 3: Find final velocity
v = v₀ + gt
v = 0 + 9.80665 × 3
v ≈ 29.42 m/s

Result: In ideal free fall, an object dropped from rest for 3 seconds falls about 44.13 m and reaches a speed of about 29.42 m/s.

Worked Example: Thrown Downward

Suppose an object is thrown downward with an initial speed of 5 m/s and falls for 2 seconds on Earth.

Step 1: Use downward as positive
v₀ = 5 m/s
t = 2 s
g = 9.80665 m/s²

Step 2: Find distance
s = v₀t + ½gt²
s = 5 × 2 + 0.5 × 9.80665 × 2²
s = 10 + 19.61
s ≈ 29.61 m

Step 3: Find final velocity
v = v₀ + gt
v = 5 + 9.80665 × 2
v ≈ 24.61 m/s

Result: Throwing the object downward increases both the distance fallen and final speed compared with simply dropping it from rest for the same time.

Worked Example: Initially Thrown Upward

Suppose an object is thrown upward with an initial speed of 10 m/s. If downward is positive, the initial velocity is:

v₀ = -10 m/s

On Earth, gravity is still positive downward:

g = 9.80665 m/s²

Step 1: Find time until velocity becomes zero at the top
v = v₀ + gt
0 = -10 + 9.80665t
t = 10 / 9.80665 ≈ 1.02 s

Step 2: Interpret the result
The object rises for about 1.02 seconds before its vertical velocity becomes zero. After that, it begins moving downward.

Important: When an object is thrown upward, displacement and total path distance are not always the same. The object may first move up, stop briefly, and then move down.

Worked Example: Compare Gravity on Earth and the Moon

Suppose an object is dropped from rest from a height of 20 m. Compare an Earth-style gravity value with a lower Moon-style gravity value.

Gravity	Time from 20 m	Final Speed	Interpretation
Earth: 9.80665 m/s²	about 2.02 s	about 19.81 m/s	Standard near-Earth ideal example
Moon example: 1.62 m/s²	about 4.97 s	about 8.05 m/s	Lower gravity gives a slower fall and lower final speed

In the ideal model, lower gravity means the object accelerates more slowly, so it takes longer to fall the same height.

How to Use This Free Fall Calculator

1. Select From height or From time mode.
2. Enter the initial vertical speed.
3. Choose the correct speed unit.
4. Enter either the vertical displacement or the elapsed time, depending on the selected mode.
5. Select a gravity preset such as Earth, Moon, Mars, Jupiter, or enter a custom gravity value if available.
6. Choose the output distance and speed units.
7. Click Calculate if the tool requires it.
8. Review the time, distance, final speed, and average speed results.

How to Interpret the Result

The calculator results describe different parts of the vertical motion.

Result	Meaning	How to Use It
Time	How long the motion lasts	Useful for comparing fall duration under different gravity values
Distance fallen	Vertical displacement during the selected interval	Useful for height-based or time-based kinematics problems
Final speed	How fast the object is moving at the end	Useful for ideal impact-speed comparisons
Average speed	Overall rate across the interval	Useful for comparing total motion rather than final instant speed

Distance, Displacement, Velocity, and Speed

Free-fall problems can involve several related but different quantities.

Quantity	Meaning	Direction Included?
Distance	Total path length traveled	No
Displacement	Change in vertical position	Yes
Speed	How fast the object moves	No
Velocity	Speed with direction	Yes

For a simple object dropped from rest and moving only downward, distance fallen and downward displacement are often the same magnitude. For an object thrown upward first, the total path distance can be greater than the net displacement.

Free Fall From Height vs Free Fall From Time

The two modes answer different kinds of questions.

Mode	Use This When You Know	Main Output
From height	Vertical displacement to the landing or reference point	Time and final speed
From time	Elapsed time of the motion	Distance/displacement and final speed

Use height mode when the problem gives a drop height. Use time mode when the problem gives how long the object has been falling or moving vertically.

Ideal Free Fall vs Real Falling Objects

The ideal free-fall model ignores air resistance. This is often fine for basic physics problems, but real objects can behave differently.

Effect	Included in This Calculator?	Why It Matters
Air resistance	No	Can reduce acceleration, final speed, and fall distance compared with the ideal model
Wind	No	Can change the path and effective speed of the object
Object shape	No	Flat or light objects can be strongly affected by drag
Rotation or tumbling	No	Can change drag and stability during the fall
Changing gravity	No	Can matter for very large height changes or orbital-scale motion

A feather, paper sheet, parachute, or skydiver will not follow the ideal no-air-resistance model closely. A compact dense object over a short fall may match the ideal model more closely, but safety analysis still needs more than a simple calculator.

Free Fall and Impact Speed

The final speed result can help show how fast an object would be moving at the end of ideal free fall. However, final speed is not the same as impact force, injury risk, or damage.

Quantity	What It Tells You	What It Does Not Tell You
Final speed	How fast the object is moving at the end of the fall	Impact force or damage
Fall time	How long the fall lasts	Whether the fall is safe
Distance fallen	Vertical displacement in the model	Real path under wind, drag, or tumbling
Impact force	Depends on stopping distance, stopping time, materials, and deformation	Not calculated by this tool

For safety, engineering, or injury analysis, use a proper impact model and professional guidance.

When This Calculator Is Useful

This calculator is useful when you need a quick ideal free-fall estimate and the assumptions match the problem.

• Physics homework and kinematics practice
• Finding time to fall from a known height
• Finding distance fallen after a known time
• Estimating final speed in ideal vertical motion
• Comparing gravity values on Earth, Moon, Mars, or Jupiter
• Learning how upward or downward initial velocity changes motion
• Checking simple one-dimensional constant-acceleration problems

When You May Need More Than This Calculator

A simple free-fall calculator may not be enough when air resistance, safety, or real-world object behavior matters.

Use a more detailed method when working with:

• skydiving or parachute motion
• objects with large air resistance
• light objects such as paper, feathers, or fabric
• high-altitude falls
• falling objects in wind
• objects that rotate, tumble, or change shape
• impact force or injury risk
• construction safety or dropped-object risk
• engineering design or safety-critical calculations
• orbital, space, or very large-distance motion where gravity changes significantly

Common Mistakes to Avoid

• Ignoring air resistance: real falling objects may fall slower than the ideal model predicts.
• Mixing up velocity and speed: velocity includes direction, while speed is only magnitude.
• Using the wrong sign for initial velocity: with downward positive, a downward throw is positive and an upward throw is negative.
• Confusing distance and displacement: they can differ when the object first moves upward and then falls.
• Using height mode for a non-vertical path: height mode should use vertical displacement, not diagonal or curved path length.
• Assuming final speed gives impact force: impact force depends on stopping distance, materials, and deformation.
• Forgetting gravity presets: the same fall height gives different results on Earth, Moon, Mars, or Jupiter.
• Using constant gravity for very large distances: gravity changes with distance in large-scale problems.

Important Assumptions and Limitations

• This calculator uses ideal one-dimensional vertical kinematics.
• It assumes constant gravitational acceleration.
• It assumes no air resistance, wind, buoyancy, drag, lift, or spin effects.
• It treats downward as positive in the standard equation explanation.
• Height mode is best understood as vertical displacement to the landing or reference point.
• From-time mode calculates ideal displacement and final velocity for the entered time.
• The calculator does not model terminal velocity.
• The calculator does not calculate impact force, injury risk, or structural damage.
• The calculator does not replace engineering, safety, workplace, construction, or medical analysis.

Practical Uses of a Free Fall Calculator

• Calculate ideal fall time from height
• Estimate ideal final speed from drop height
• Find distance fallen after a certain time
• Compare falls under different gravity values
• Practice kinematic equations
• Understand upward and downward initial velocity
• Prepare for projectile motion, kinetic energy, and impact-energy topics
• Check classroom examples quickly

References

1. OpenStax University Physics Volume 1: Free Fall
2. OpenStax College Physics 2e: Falling Objects
3. OpenStax Physics: Motion and Kinematics Background
4. NIST CODATA: Standard Acceleration of Gravity

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• Projectile Motion Calculator
• Velocity Calculator
• Acceleration Calculator
• Kinetic Energy Calculator
• Potential Energy Calculator

Frequently Asked Questions

What is free fall?

Free fall is motion under gravity alone. In the ideal model, air resistance and friction are ignored, so gravity is the only acceleration acting on the object.

What formula does the Free Fall Calculator use?

The main formulas are s = v₀t + ½gt² for displacement and v = v₀ + gt for final velocity.

What is the gravity value on Earth?

A common standard gravity value is 9.80665 m/s². Many classroom examples round this to 9.8 m/s².

How do I find time from height?

For an object dropped from rest, use t = √(2s / g). If the object has an initial vertical velocity, use the full kinematic equation instead.

How do I find distance from time?

Use s = v₀t + ½gt². If the object starts from rest, this simplifies to s = ½gt².

How do I find final speed in free fall?

Use v = v₀ + gt when time is known, or v² = v₀² + 2gs when displacement is known.

Does this calculator include air resistance?

No. This calculator uses the ideal no-air-resistance model. Real falling objects can be slowed by drag, wind, shape, and rotation.

Why does gravity change the result?

Gravity controls acceleration. Higher gravity increases final speed faster and usually reduces fall time for the same height. Lower gravity makes the fall slower in the ideal model.

Can initial velocity be negative?

Yes. If downward is treated as positive, a negative initial velocity means the object is initially thrown upward.

Is free-fall final speed the same as impact force?

No. Final speed tells you how fast the object is moving at the end of the fall. Impact force depends on stopping distance, stopping time, materials, deformation, and other factors.

Can I use this calculator for skydiving or parachutes?

No. Skydiving and parachute motion are strongly affected by air resistance and terminal velocity. This calculator is for ideal free-fall estimates only.

Disclaimer: This Free Fall Calculator provides educational estimates for ideal vertical motion under constant gravity. It assumes no air resistance, no wind, no drag, no buoyancy, no rotation effects, and no change in gravity during the fall. Results depend on the initial vertical speed, height or time entered, gravity value, direction convention, and selected units. The calculator is best for textbook-style free-fall and kinematics problems, not real-world impact safety, skydiving, parachutes, dropped objects with large air resistance, high-altitude falls, or engineering risk analysis. A positive or negative initial velocity depends on the chosen direction convention, and height mode should be treated as vertical displacement to the landing/reference point. Use this calculator for homework, learning, and general comparisons, and use a full physics, engineering, or safety model for real falling objects, injury risk, structural safety, equipment design, or high-stakes applications.