Four-factor Formula Calculator
☢ Nuclear & Decay. Use the Four-factor formula formula to find multiplication k∞, fast fission ε, resonance escape p, thermal use f, reproduction η: pick the value you want, type the others, and the answer updates as you go.
k > 1 means the chain reaction grows.
Pick the ○ next to the value you want to find, fill in the others, and it solves as you type.
What each letter means
| Quantity | Unit |
|---|---|
| Multiplication k∞ | no unit |
| Fast fission ε | no unit |
| Resonance escape p | no unit |
| Thermal use f | no unit |
| Reproduction η | no unit |
Worked example
Find the multiplication k∞ when Fast fission ε = 1.03, Resonance escape p = 0.87, Thermal use f = 0.71, Reproduction η = 1.65.
Using k_∞ = ε p f η: Multiplication k∞ = 1.0498.
Frequently asked questions
What is the formula for Four-factor formula?
k_∞ = ε p f η. k > 1 means the chain reaction grows.
What do the letters stand for, and what units are used?
Multiplication k∞, Fast fission ε, Resonance escape p, Thermal use f, Reproduction η.
How do you calculate multiplication k∞?
Put the values into k_∞ = ε p f η. For example, with Fast fission ε = 1.03, Resonance escape p = 0.87, Thermal use f = 0.71, Reproduction η = 1.65, multiplication k∞ = 1.0498.
Can I solve for a different value?
Yes. In the calculator above, pick the circle next to any value (multiplication k∞, fast fission ε, resonance escape p, thermal use f, reproduction η) and fill in the others: it rearranges the formula for you.
