22 calculators · No login · No tracking beyond ad cookies
ProbLab turns abstract formulas into interactive tools with visualizations and plain-English interpretation — so you can actually use the result, not just compute it.
Each tool shows the math, draws a chart, and explains what the number actually means.
Updated Sep 2026
Multi-dice (d4–d100), exploding dice, critical hits, D&D 5e advantage. With comparison chart.
Streak probability, longest-run expected value, Markov chain visualization.
5- and 7-card hand ranking + equity vs. random hands. With board texture hints.
Pass / Don't Pass / Odds bets. Dice combination heatmap and house edge breakdown.
European vs. American wheel, custom bet patterns, martingale ruin curve.
Collision probability for any group size with a heatmap and 50% threshold.
Win/tie/lose probability, expected duration, and ruin curve across bankrolls.
Drawing without replacement — lottery tickets, blackjack, quality sampling.
Sequential multi-evidence updates with prior/posterior chart. Medical-test presets included.
Run N trials, watch switch vs. keep converge, and explore the "host-knows" variants.
Customer arrivals, server queues, incident rates — with staffing recommendation.
Multi-outcome EV with tornado sensitivity chart — answers "is this bet worth it?"
Dataset input + histogram + Chebyshev bound visualization.
Z-score, percentile, two-tailed p-value with a shaded bell curve.
For means & proportions with required-sample-size calculator for A/B tests.
Contingency table input, χ² stat, p-value, df lookup, and effect-size phi.
Optimal bet size with growth-curve simulation and fractional-Kelly comparison.
N-step transition probabilities and stationary distribution.
Sample from Normal / Exponential / Beta / Gamma and inspect the histogram.
Hot/cold number visualization. Includes a gambler's-fallacy debunker.
Hit / Stand / Double / Split recommendations for hard and soft totals.
Build probability trees for dependent events — multi-branch visualization.
P(X=k), P(X≤k), P(X≥k), normal approximation vs. exact, and chart.
Most calculator sites hand you a number with no context. ProbLab treats probability as a decision-support problem, not a math drill.
Every tool draws a chart inline (canvas-based, no external libs) so you can see the distribution, not just trust a number.
Each result comes with "what this number means in practice" — for whom the bet is worth it, when to ignore it, and the obvious pitfalls.
We publish the math assumptions (independence, infinite bankroll, no-memory, etc.) so you know exactly where the result breaks.
ProbLab is an independent calculator suite built by a small team of statisticians, tabletop gamers, and educators who got tired of probability widgets that return a single floating-point number and call it a day.
Found a bug or a math error? Email us — we fix reported mistakes within a week.