Explore the Force, Energy and Pressure Behind Your Techniques
🥋 Start here — Explore the Physics of a Taekwon-Do Strike
How hard does a punch or kick hit — and what determines the impact?
This calculator lets you explore the physics behind a Taekwon-Do strike.
You do not need to know any physics or do any calculations yourself.
Choose a technique, enter a few details, and the calculator does the rest.
How to use the calculator
Choose your technique — for example, forefist punch, side piercing kick or turning kick.
Enter your body mass — the calculator estimates how much effective mass contributes to the strike.
Keep the suggested values or experiment — you can change strike speed, contact area and effective impact/deformation distance.
Press Calculate Strike.
Start with the headline results — especially average force, estimated peak force, energy and pressure. Then scroll down if you want to see the physics behind them.
What should I look at first? Force tells you how strongly the strike pushes on the target.
Peak force estimates the largest force during the very short impact.
Energy tells you how much kinetic energy the strike carries.
Pressure tells you how concentrated the force is — the same force delivered through a smaller striking area produces greater pressure.
Want the physics?
Keep scrolling after the results. The sections below explain momentum, impulse, collision time,
force, energy and pressure step by step, together with the assumptions and references used.
Strike inputs
Enter the effective striking mass and its motion immediately before contact with the board or block.
Selecting a technique loads teaching defaults for impact velocity and contact area. Effective striking mass is estimated as a technique-dependent fraction of practitioner body mass; all values remain editable.
Striking tool: Forefist (Ap Joomuk) • Effective mass model: 3.75% of body mass • Estimated contact area: 6 cm²
Press Calculate Strike to visualise contact →
kg
The default effective striking mass scales with practitioner body mass for all listed techniques. The forefist default effective striking mass is 3.0 kg for an 80 kg practitioner (3.75% of body mass).
kg
Effective mass of the fist/foot/limb participating in the impact.
m/s
mm
Crumple-zone analogy: Skin, soft tissue, joints and the target deform as the coupled striking mass decelerates. This is the effective deceleration distance, not simply board penetration or the thickness of compressed skin. The 20 mm punch / 30 mm kick defaults are illustrative sensitivity assumptions, not experimentally measured or calibrated values.
cm²
Approximate effective area of the striking tool carrying the impact load. Technique defaults are teaching estimates, not measured constants, and are manually editable.
Calculated results
Force is shown in newtons (N) and, beneath the force value, as an equivalent weight in kilograms (kgf). For example, 981 N is approximately the weight of a 100 kg mass on Earth. This does not mean the strike has a mass of 100 kg.
Initial momentum
3.50 kg·m/s
Magnitude before impact
Impulse from board
3.50 N·s
Opposite to the incoming motion
Collision time
2.40 ms
Constant-deceleration estimate
Average force
1.46 kN
≈ 212 × the striking mass's weight
Estimated peak force
2.92 kN
2 × average force; triangular force–time pulse assumption
Average contact pressure
2.92 MPa
Average force ÷ contact area
Estimated peak pressure
5.83 MPa
Estimated peak force ÷ contact area
Kinetic energy at impact
8.75 J
½mv² immediately before contact
Selected technique
Forefist punch (Ap Joomuk Jirugi)
Uses your custom physical inputs
Pressure and the striking surface
For the same force, a smaller contact area produces greater local pressure:
P = F / A
This helps explain why martial arts use well-defined striking surfaces. It does not mean pressure alone determines whether a board breaks: board bending, grain, thickness, support, material strength, impact position and energy also matter.
20 cm²0 MPa
10 cm²0 MPa
5 cm²0 MPa
2 cm²0 MPa
Comparison above holds the current estimated peak force constant and changes only contact area.
MODEL ASSUMPTION
Force–time pulse
The strike inputs determine the impulse (the area under the force–time curve), but not the exact shape of that curve. For an educational estimate, this calculator assumes a triangular force pulse: force rises from zero to a peak and then falls back to zero. A triangle with the same impulse and collision time has Fpeak = 2Favg.
The dashed horizontal line is the average force. The triangle has the same area (impulse) as a constant-force rectangle at Favg.
Board / block threshold comparison
Optional: enter a force threshold supplied by your experiment, manufacturer or teaching exercise. This is a simple comparison—not a prediction of real board fracture.
Reference point — standard pine board:
Breaking a standard 1-inch white pine board (typically 12×12 or 12×6 inches) can be taken here as a reference peak impact force of 1,300–3,100 N (1.3–3.1 kN).
Important: this reference is a peak force range. The calculator compares it with an estimated peak force obtained by assuming a triangular force–time pulse. This is a model-based estimate, not a measured peak force.
N
Quick reference values:
Step-by-step calculation
1. Impulse = change in momentum
|J| = m v = (0.70)(5.0) = 3.50 N·s
2. Estimate the collision time
vavg = (5.0 + 0)/2 = 2.50 m/s Δt = d/vavg = 0.006/2.50 = 0.00240 s = 2.40 ms
P = F/A. For A = 5.0 cm² = 0.000500 m²: Pavg ≈ 2.92 MPa Ppeak,est ≈ 5.83 MPa
Physics model
ImpulseJ = Δp = m(vf − vi)
Stopping timeΔt = 2d / v
Average forceFavg = mv² / 2d
Impact energyEk = ½mv²
Peak-force estimateFpeak ≈ 2Favg
Contact pressureP = F / A
Textbook references for the equations: The fundamental relationships used here are covered in OpenStax, University Physics, Volume 1 (Ling, Sanny & Moebs, 2016): §9.2 Impulse and Collisions (momentum, impulse, average force and force–time area); §3.4 Motion with Constant Acceleration (average speed and Δt = 2d/v when slowing uniformly to rest); §7.2 Kinetic Energy and §7.3 Work–Energy Theorem (E = ½mv² and Favg = mv²/2d under the model assumptions); §14.1 Pressure (force per unit area; used here as nominal average contact pressure). Model-specific approximation: Fpeak,est ≈ 2Favg follows from assuming a triangular force–time pulse with the same impulse; it is not a universal textbook law or an experimentally validated peak-force formula.
Model assumptions: the striking mass travels in one dimension and decelerates uniformly from its impact velocity to rest over the entered stopping distance. This gives the average collision force from impulse divided by collision time. The calculator also reports an estimated peak force: because mass, velocity and stopping distance alone do not determine the true force–time profile, the impact is approximated as a triangular force–time pulse. The area under this triangle must equal the impulse, so its peak is twice its average height: Fpeak,est ≈ 2Favg. This peak value is therefore a model-based estimate, not a directly measured peak force. Real Taekwon-Do strikes involve deformation of the target and body, changing effective mass, non-uniform force, and—in a successful break—continued motion through the target. The effective deceleration distance includes compliant deformation of both striker and target; it is not measured directly here. The 20 mm punch and 30 mm kick defaults are illustrative rather than literature-calibrated. Contact duration is not necessarily the stopping time, especially when the foot continues pushing on the target. Uniform deceleration and a triangular contact-force pulse are separate approximations, so the displayed peak is a scenario estimate rather than a self-consistent dynamical prediction. The default effective striking mass is a teaching estimate that scales with practitioner body mass: forefist punch 3.75%, front snap kick 25%, turning kick 20%, and side/back piercing kicks 37.5%. At 80 kg these give 3, 20, 16 and 30 kg respectively. These percentages represent effective/coupled striking mass rather than simply anatomical limb mass. This calculator is intended as an educational mechanics model.
Impact distance: sensitivity and experimental context
At fixed effective mass and velocity, doubling the assumed effective deceleration distance halves the calculated average force. For a 3 kg forefist at 5 m/s, the model gives 6.25 kN at 6 mm, 1.88 kN at 20 mm and 1.50 kN at 25 mm. The triangular-pulse peak estimate is twice these values.
Why not fit distance directly to published peak forces? Published experiments use different targets, velocities, definitions of effective mass and force-pulse shapes. A measured peak force alone cannot establish an effective stopping distance without a compatible impulse/energy model. Contact time is not necessarily the time to stop.
Selected published context: Góra et al., Applied Sciences (2024), report median peak forces of 2.66 kN for turning kicks and 4.60 kN for side kicks in four ITF practitioners. Wąsik et al., Physical Activity Review (2023), report approximately 1.18 kN for a straight punch and 2.01–2.41 kN for kicks from a single practitioner, with contact times varying markedly by technique. These are measurements on specific instrumented targets, not validated board-breaking thresholds or directly interchangeable inputs to this model.
