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).
Function values at equally spaced x; separate with commas or spaces.
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
- I = h/3 [y₀ + 4(y₁ + y₃ + …) + 2(y₂ + y₄ + …) + yₙ]
- n = 4 intervals, h = 0.25
- 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):
- I = h/3 [y₀ + 4(y₁ + y₃ + …) + 2(y₂ + y₄ + …) + yₙ]
- n = 4 intervals, h = 0.25
- I ≈ 0.785392
Trapezoidal rule: 0.782794 · Simpson’s 1/3 rule: 0.785392 · Simpson’s 3/8 rule: needs n divisible by 3
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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.
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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/