Enter fall and stopping details
Use measured values where possible. Conservative assumptions improve safety screening.
Formula used
The model first finds impact energy after the selected loss allowance. It then converts that energy into average contact force.
Here, m is mass, g is gravity, h is height, L is energy-loss fraction, d is stopping distance, and t is stopping time.
How to use this calculator
- Enter the total mass that actually falls.
- Enter vertical fall height and select the correct unit.
- Choose Earth, another gravity condition, or a custom value.
- Allow for energy lost before contact, when appropriate.
- Select stopping distance or stopping time.
- Use a conservative peak multiplier and safety factor.
- Calculate, then compare average, peak, and design forces.
Example data
| Input | Example value | Why it matters |
|---|---|---|
| Mass | 75 kg | Sets the weight and stored fall energy. |
| Fall height | 2.0 m | Sets ideal impact speed and energy. |
| Stopping distance | 0.05 m | Represents 50 mm of effective compression. |
| Peak multiplier | 2.0× | Allows for a non-uniform stopping force. |
| Safety factor | 1.5× | Provides a conservative equipment comparison value. |
Fall Impact Loads
Why Fall Impacts Matter
A fall converts height into speed. The final stop creates serious load. A person, tool, or object carries energy before contact. The same fall can create different forces. Surface softness matters. A thick mat increases stopping distance. A rigid floor provides almost none. That difference changes average contact force greatly. Mass also matters. Heavier objects contain more energy at one height. Greater height raises energy and impact speed. Gravity changes both values. Air drag and harness effects can remove energy. The energy-loss field models that reduction. Impact force is not one perfect value. Real contact force rises and falls during stopping. The calculator reports average contact force. It estimates peak force with a load-shape multiplier. This gives a planning range. It does not replace certified safety analysis.
Energy, Speed, and Stopping
Before impact, gravitational potential energy is mgh. The letters represent mass, gravity, and fall height. The calculator adjusts energy for selected losses. Remaining energy becomes impact kinetic energy. Impact speed follows from that energy. Stopping distance is often the most useful input. A helmet liner, airbag, rope, foam pad, or crushed structure extends the stop. Added distance reduces force. In distance mode, average contact force includes object weight. It equals impact energy divided by stopping distance, plus weight. Stopping time is another option. It may come from sensor data or an arrest device. The calculator uses momentum change across the selected time. It adds object weight. It estimates average stopping distance. Both modes are simplified. They assume controlled average deceleration. Abrupt impacts can create larger peaks.
Reading the Calculated Values
Impact speed compares hazards. It is shown in m/s and km/h. Impact energy is shown in joules. That energy must be absorbed. Average contact force is the surface force estimate. Peak force uses the chosen multiplier. Gentle stops need less. Sharp stops need more. Use test data. The design force adds a safety factor. This helps select rated equipment. Equivalent g-load compares contact force with normal weight. It is useful, but can mislead. A high g-load lasting milliseconds differs from one lasting longer. Material limits depend on direction. Human tolerance depends on position. Treat output as an estimate. Verify critical decisions with review.
Choosing Safer Assumptions
Use consistent inputs. Enter falling mass. Include attached equipment. Measure height from the centre of mass. Use realistic stopping distance. Do not use surface thickness alone. Actual compression matters more. Select a conservative energy-loss value. Low loss assumes more energy reaches the stop. Select a higher peak multiplier for hard landings. Select a safety factor for rules. Results become more cautious with higher values. Compare several cases. Try concrete, padding, rope arrest, and controlled deceleration. Small improvements in stopping distance can greatly reduce force. Document assumptions. This calculator supports early design education. It cannot certify fall protection equipment. Follow standards and limits for installations.
Frequently asked questions
1. Does this calculator show an exact impact force?
No. It estimates average and peak loading from simplified energy or momentum models. Real impacts depend on material stiffness, changing deceleration, angle, posture, and contact geometry.
2. Why does stopping distance matter so much?
The same impact energy spread across a longer distance requires less average force. Foam, airbags, ropes, and crush structures work by increasing that stopping distance.
3. What stopping distance should I enter?
Enter actual effective compression or arrest travel. Use the distance over which the object slows, not merely the visible thickness of padding or equipment.
4. What does the energy-loss percentage represent?
It represents energy removed before final impact. Examples include air drag, friction, controlled descent, rope stretch, or another earlier energy-absorbing process.
5. When should I use stopping time?
Use stopping time when sensor data, test data, or device specifications provide a reliable arrest duration. Distance mode is usually more intuitive for compression materials.
6. What peak multiplier is appropriate?
Use measured data where available. A multiplier near one represents a smoother stop. Higher values represent sharper, less uniform impacts. Conservative design often needs a higher value.
7. Is equivalent g-load the same as deceleration?
Not exactly. Equivalent g-load compares contact force with normal weight. Net deceleration excludes the weight component and describes the speed reduction more directly.
8. Can I use this for fall-arrest equipment selection?
Use it for preliminary comparisons only. Do not use it as equipment certification. Follow manufacturer instructions, applicable standards, and qualified engineering guidance for real installations.
9. Does body position affect injury risk?
Yes. The same force can have different outcomes depending on body orientation, contact area, restraint geometry, duration, and the body region receiving the load.
10. Can the calculator work for dropped tools?
Yes. Enter the tool mass, drop height, and realistic stopping distance or time. This can help compare protective mats, catch systems, and containment options.
11. Why is the safety-adjusted force larger?
The safety-adjusted force multiplies estimated peak force by your chosen safety factor. It creates a more conservative comparison value for planning and preliminary design.