Steady State Probability Calculator

Iterate a Markov chain until it approaches a steady-state distribution. This educational calculator shows the formula, result, and step-by-step interpretation.

ProbabilityComputer Science

Calculator

What this calculator teaches

Steady-state probabilities describe long-run behavior in Markov chains and stochastic systems.

Use the result as a learning aid. For classwork, still show the formula and intermediate reasoning so the final answer is not just a black-box number.

What a Steady-State Distribution Means

For a Markov chain with transition matrix P, a steady-state row vector π satisfies πP = π. Its entries are long-run state proportions when the chain converges. Starting from an initial probability row vector v0, repeated multiplication produces v1 = v0P, v2 = v1P, and so on. This calculator performs that iteration a chosen number of times.

A valid transition matrix normally has nonnegative entries and each row sums to 1. Each row describes the probabilities of moving from one current state to all possible next states. A probability state vector should also have nonnegative entries totaling 1. Under common conditions such as irreducibility and aperiodicity in a finite chain, repeated multiplication converges to a unique stationary distribution regardless of the starting distribution.

QuantityRuleMeaning
One stepvₖ₊₁ = vₖPAdvance the distribution one transition
After n stepsvₙ = v₀PⁿDistribution after repeated transitions
Steady stateπP = πDistribution unchanged by another step

Not every chain has one attracting steady state. An identity matrix, for example, leaves every initial distribution unchanged, while periodic chains can oscillate rather than settle. Iteration should therefore be interpreted together with the structure of P.

Algebraically, a stationary distribution is a left eigenvector of P associated with eigenvalue 1, normalized so its entries sum to 1. Iteration is an intuitive numerical route; solving πP=π together with Σπᵢ=1 is the corresponding equation-based route.

Formula & Symbols

ConceptFormula or rule
Steady stateπ = πP

Worked example

Example: After many steps, some Markov chains settle near a stable distribution.
Example 2: For P = [[0.8,0.2],[0.3,0.7]], the stationary distribution is [0.6,0.4]. Multiplying [0.6,0.4] by P returns [0.6,0.4].
Example 3: For P = [[0.9,0.1],[0.2,0.8]], the stationary distribution is [2/3,1/3] ≈ [0.6667,0.3333].
Example 4: If both rows are [0.5,0.5], any starting distribution becomes [0.5,0.5] after one transition.
Example 5: With the identity matrix [[1,0],[0,1]], every starting vector is stationary, so there is no single attracting distribution selected by iteration.

Common mistakes

⚠️
Using the wrong input format

Keep lists comma separated, matrices as rows separated by semicolons, and modular inputs as integers.

⚠️
Ignoring assumptions

Some methods require positive probabilities, valid moduli, independent trials, or small educational input sizes.

⚠️
Using rows that do not sum to 1

A probability transition matrix should have each row total 1; otherwise repeated multiplication no longer represents ordinary state probabilities.

⚠️
Assuming iteration always converges

Reducible or periodic chains can retain dependence on the starting state or oscillate. Convergence is a property of the chain, not just the iteration count.

FAQ

Can I use decimals?
Most numerical calculators allow decimals, but modular arithmetic and coding-theory tools usually require integers or binary strings.
Is this for homework checking?
Yes. The page is designed to show both the answer and the reasoning pattern.
Why does the result sometimes say approximate?
Some probability, floating-point, and numerical methods naturally produce approximations.
How many iterations should I use?
Increase the iteration count until successive vectors change only by the tolerance you need. Slow-mixing chains may require many more iterations than simple two-state examples.
Does the starting distribution matter?
For an ergodic finite chain with a unique attracting stationary distribution, the long-run limit does not depend on the starting distribution. For other chains, it can matter.
What is the difference between stationary and limiting?
A stationary distribution satisfies πP = π immediately. A limiting distribution is what repeated transitions approach. A stationary distribution can exist even when some starting distributions do not converge to it.
How can I verify a candidate steady state?
Check that its entries are valid probabilities and multiply the row vector by P. If the product equals the original vector within rounding tolerance, it is stationary.

Related calculators

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Formula Explorer connections

Interpretation: This formula summarizes data, models uncertainty or supports inference about a population or random process. Assumption: The sampling design and distribution assumptions must match the data. Independence, sample size, outliers and measurement quality can materially affect interpretation.

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