Advanced Penetration Inputs
Penetration Graph
The chart compares estimated shell penetration against total effective armor from 1 km to 30 km.
Example Data Table
| Scenario | Shell | Armor | Angle | Range | Use Case |
|---|---|---|---|---|---|
| Battleship belt test | 406 mm AP | 350 mm | 35° | 15 km | Heavy belt penetration check |
| Cruiser bow test | 380 mm AP | 27 mm | 60° | 12 km | Overmatch and ricochet check |
| Destroyer plating test | 127 mm HE | 19 mm | Any | 8 km | HE shatter or penetration check |
Formula Used
Remaining velocity = muzzle velocity × e^(-velocity decay × range)
AP penetration = K × caliber^0.65 × shell weight^0.50 × remaining velocity^1.10
Corrected angle = max(impact angle - normalization, 0)
Effective armor = armor thickness / cos(corrected angle)
Overmatch occurs when shell caliber > 14.3 × armor thickness
HE penetration = shell caliber × HE coefficient × optional bonus
The De Marre coefficient is adjustable. Use it to tune the calculator against trusted reference data. The result is best treated as a mathematical estimate for one shell and one armor plate.
How to Use This Calculator
- Enter shell caliber, weight, velocity, and range.
- Add target armor thickness and impact angle.
- Choose shell type and hit zone.
- Adjust normalization, ricochet limits, and HE coefficient if needed.
- Press Calculate to view the result above the form.
- Use CSV or PDF export for saved comparisons.
About this Penetration Estimator
Why penetration math matters
Armor penetration is a useful way to compare a shell, an angle, and a plate before making a shot decision. This calculator gives a structured estimate. It is not an official game engine. It is a planning tool for learning why a shell may punch through, bounce, shatter, or arm too early.
Velocity and range
The first part of the model estimates remaining shell speed at range. A higher range usually lowers velocity. Lower velocity then reduces estimated armor piercing power. The page uses a De Marre style curve because it is simple, adjustable, and easy to tune for different shell families. You can change the coefficient when your own test data suggests another value.
Angle and effective armor
The second part handles armor angle. A flat hit has a short path through the plate. A steep hit has a longer path. Normalization reduces that steepness for armor piercing shells. The adjusted angle is used to calculate effective armor. A plate that is 200 mm thick can behave like a much thicker plate when it is angled hard.
Ricochet and overmatch
The third part checks ricochet and overmatch. Ricochet limits can be changed because shells may not share identical rules. Overmatch compares shell diameter with plate thickness. When the shell is large enough, the plate cannot force a normal ricochet. The calculator still shows effective thickness and fuse arming data, because shell behavior after the first plate can remain important.
Damage estimate
The fourth part estimates likely damage. Penetrations, over-penetrations, citadel hits, and saturation do not return the same value. The damage field lets you study possible hit value, not only raw penetration. This is useful when comparing a safe broadside shot against a steep angled target.
Scenario testing
Use the example table to learn common patterns. Then enter your own shell data. Try several ranges. Watch the Plotly chart change. A good result is not just a green label. A good result has enough penetration margin, low bounce chance, and a fuse behavior that matches the target zone.
Practical caution
For best use, treat every output as a scenario. Real battles include dispersion, impact point, hidden armor, water drag, and layered geometry. Run several nearby values before choosing your aim point during combat conditions safely.
FAQs
1. Is this an official penetration calculator?
No. It is an educational estimator. It uses adjustable math to model common armor behavior, but it cannot copy every hidden game rule.
2. What does impact angle mean?
It is the angle from the armor plate normal. Zero degrees means a flat hit. Higher values mean a steeper, harder hit.
3. What is effective armor?
Effective armor is the thickness a shell must cross after angle is considered. Angled armor can behave much thicker than its listed value.
4. What does overmatch mean here?
Overmatch means the shell is large enough to avoid normal ricochet on that plate. The calculator still shows fuse and margin data.
5. Why can penetration margin be negative?
A negative margin means the estimated penetration is below the calculated armor requirement. That usually indicates a bounce, shatter, or stop.
6. Why is the De Marre coefficient editable?
Different shells can behave differently. The coefficient lets you tune the curve against your own test data or preferred reference values.
7. Does HE use impact angle?
This calculator treats HE as a direct threshold check. It compares HE penetration against armor thickness and optional spaced armor.
8. Why does the graph stop at 30 km?
Thirty kilometers keeps the graph readable for most naval gun scenarios. You can change the loop in the code for a wider range.