Math and Statistics

  • D&D Advantage / Disadvantage Dice Calculator
    Calculate your chance to hit a d20 target number with Advantage, Disadvantage, or a normal roll in Dungeons & Dragons 5e.
  • Lottery Expected Value Calculator
    Calculate the expected value of a lottery ticket from the jackpot, odds, and ticket price. See if a ticket is worth it in the long run.
  • Exact Binomial Test Calculator
    Compute the exact binomial test p-value (two-sided and one-sided) for k successes in n trials against a hypothesized probability p.
  • Solve and Graph Inequalities Calculator
    Solve linear inequalities ax + b ≤ c (and <, ≥, >) instantly. Get the boundary value, direction, and interval notation for the number line.
  • Confidence Interval for Difference of Two Proportions
    Compute a confidence interval for the difference between two sample proportions (p̂₁−p̂₂) at 90%, 95%, or 99% using the normal approximation.
  • Long Division Calculator
    Free long division calculator: enter a dividend and divisor to get the quotient, remainder, and decimal result instantly using a = b·q + r.
  • Occupancy Rate Calculator
    Calculate occupancy rate as a percentage for hotels, rentals, parking, and venues. Enter occupied and total units to get occupancy and vacancy %.
  • Simple Interest Percentage (Rate) Calculator
    Find the simple interest rate as a percentage from principal, interest earned, and time. Rate = (I / (P x T)) x 100. Free, instant, accurate.
  • Solve for y Calculator
    Solve for y in a linear equation Ax + By = C. Enter A, B, C and x to instantly isolate y, plus get the slope and y-intercept. Free online tool.
  • Multi-Step Equation Calculator
    Solve linear equations of the form ax + b = cx + d for x. Enter the four coefficients and get the exact step-by-step solution instantly.
  • Round to n Significant Figures Calculator
    Round any number to a chosen number of significant figures and view its scientific-notation form (mantissa and exponent). Free, instant, and accurate.
  • Law of Total Probability Calculator
    Compute P(A) from conditional and partition probabilities using the law of total probability: P(A) = Σ P(A|Bᵢ)·P(Bᵢ). Supports up to 3 events.
  • Confidence Interval for Difference of Two Means Calculator
    Compute a confidence interval for the difference between two independent sample means using the Welch t-method. Enter means, SDs, sizes and confidence level.
  • Polynomial from Roots Calculator
    Build and expand a polynomial P(x) from its real roots. Enter zeros and a leading coefficient to get the full expanded form, degree, and constant term.
  • Sample Size from Margin of Error Calculator
    Calculate the survey sample size needed for a target margin of error and confidence level using n = z² p(1−p)/E², with optional finite population correction.
  • Shannon Entropy Calculator
    Compute Shannon entropy H = -Σ pᵢ·log₂(pᵢ) from a probability distribution. Supports bits, nats and dits, plus max entropy and efficiency.
  • Cohen's Kappa Calculator
    Calculate Cohen Kappa (κ) for inter-rater agreement from a 2x2 table. Get observed and expected agreement and interpret reliability instantly.
  • Average Speed Calculator (Two Trips)
    Calculate average speed across two trips using total distance divided by total time. Enter distances and times to get the true overall speed.
  • Simplify Fraction Calculator
    Simplify any fraction to its lowest terms using the greatest common factor (GCF). Get the reduced fraction, GCF, decimal value, and mixed number instantly.
  • Percent of Budget Spent Calculator
    Find what percentage of your budget you have spent. Enter your total budget and amount spent to see percent used, percent remaining, and money left.
  • Percent of Goal Achieved Calculator
    Calculate the percent of goal achieved (quota attainment) by dividing actual by target. See attainment %, amount remaining, and % left to goal.
  • Parallel or Perpendicular Lines Checker
    Check if two lines are parallel, perpendicular, or neither by comparing their slopes. Enter m₁ and m₂ to get an instant answer with the product.
  • Average of Two Numbers (Midpoint Value) Calculator
    Find the average (midpoint) of two numbers instantly with average = (a + b) / 2. Also shows the amplitude (half-range) between the values.
  • Percent Decrease From X to Y Calculator
    Calculate the percent decrease from a starting value X to an ending value Y. Enter both numbers to get the percentage drop and absolute change instantly.

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