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    Simpson’s Rule Calculator

    Simpson’s 1/3 rule weights the ordinates 1, 4, 2, 4 … 1 and multiplies by h/3: for 1/(1 + x²) from 0 to 1 with h = 0.25 the integral is 0.785392 (exact value π/4 = 0.785398).

    Rule:

    Function values at equally spaced x; separate with commas or spaces.

    Integral I ≈

    0.785392

    Full answer, then cut to fewer decimals (not rounded):

    • 0.785392
    • 0.78539
    • 0.7853
    • 0.785
    • 0.78
    • 0.7
    Intervals n
    4
    Trapezoidal rule
    0.782794
    Simpson’s 1/3 rule
    0.785392
    Simpson’s 3/8 rule
    needs n divisible by 3
    Step-by-step solution
    1. I = h/3 [y₀ + 4(y₁ + y₃ + …) + 2(y₂ + y₄ + …) + yₙ]
    2. n = 4 intervals, h = 0.25
    3. I ≈ 0.785392

    Simpson’s Rule Formula

    I = h/3 [y₀ + 4(y₁ + y₃ + …) + 2(y₂ + y₄ + …) + yₙ]

    h step size, n even number of intervals

    Worked Example

    y = 1/(1 + x²) at x = 0, 0.25, …, 1 (h = 0.25):

    1. I = h/3 [y₀ + 4(y₁ + y₃ + …) + 2(y₂ + y₄ + …) + yₙ]
    2. n = 4 intervals, h = 0.25
    3. I ≈ 0.785392

    Trapezoidal rule: 0.782794 · Simpson’s 1/3 rule: 0.785392 · Simpson’s 3/8 rule: needs n divisible by 3

    More Engineering Mathematics Calculators

    Frequently asked questions

    When can Simpson’s 1/3 rule be used?

    Only with an even number of intervals (an odd number of ordinates). Simpson’s 3/8 rule needs a multiple of three intervals; the trapezoidal rule works with any number.

    What is the error order of Simpson’s rule?

    Simpson’s 1/3 rule is exact for cubics; its error is of order h⁴. The trapezoidal rule is exact for straight lines with error of order h².

    Sources

    Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.

    Cite this page

    APA

    Scientific Converters. (2026, October 15). Simpson’s Rule Calculator. Retrieved October 25, 2026, from https://scientificconverters.com/calculators/simpsons-rule-calculator/

    IEEE

    Scientific Converters, "Simpson’s Rule Calculator," scientificconverters.com. Accessed: Oct. 25, 2026. [Online]. Available: https://scientificconverters.com/calculators/simpsons-rule-calculator/

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