Math & Scientific
Integral Calculator
Integral: integral Calculator estimates the definite integral numerically (Simpson-style) between the limits you enter. Worked through below with real figures, and the calculator repeats the working on your own inputs — free, on-device, instant.
Integral Calculator lets you estimate a definite integral in seconds: enter your expression in x, from a and to b for the area under the curve, all worked out locally in your browser.
About this calculator
It matters when you need the exact relationship checked quickly rather than worked through by hand. The governing relationship: Integral Calculator estimates the definite integral numerically (Simpson-style) between the limits you enter. See it on real numbers: ∫ 2x dx = x² + C; evaluated from 0 to 3 it is 3² − 0 = 9 . The calculator above applies the same steps to whatever you enter — computed locally, nothing sent anywhere.
How to use
- Type the function of x you want to integrate, for example x^2 + 3x + 2.
- Enter the lower limit a and the upper limit b.
- Press Calculate to estimate the definite integral.
- Read the approximate area under the curve between a and b.
Why use Integral Calculator
Fast
Calculations run in your browser. No round trip to a server.
Private
Your inputs never leave your device. Nothing is uploaded.
Free
No signup, no paywall, no ads-in-results, no watermarks.
Accurate
Numerical estimates, with the method shown in each result.
Mobile-ready
Optimised for phones, tablets, and desktops alike.
Transparent
Honest disclaimers wherever browser limits or regional rules apply.
Common uses
Use it for quick mental-math cross-checks
Use it for verifying answers from a textbook
Use it when revising for exams
Integral in competitive-exam practice
Use it for double-checking a spreadsheet result
Use it when working through problems
Technical notes
Integral Calculator estimates the definite integral numerically (Simpson-style) between the limits you enter.
Inputs are taken exactly as entered, so check for typos before trusting an answer.
Nothing you type is uploaded — the calculation happens entirely on your device.
FAQ
How is the integral calculated?
It uses Simpson's rule with 1000 subintervals to approximate the definite integral numerically; it is not a symbolic integrator.
Can a be larger than b?
Yes. If the lower limit is greater than the upper limit, the result is the signed integral, which simply carries the opposite sign.
Which functions are supported?
Use +, minus, *, /, ^ and functions like sin, cos, exp, ln and sqrt, with x as the variable. Implicit multiplication such as 3x is accepted.
Does the Integral Calculator send my data to a server?
No. The Integral Calculator runs entirely in your browser, so nothing you enter is uploaded, stored, or shared.
Worked example
∫ 2x dx = x² + C; evaluated from 0 to 3 it is 3² − 0 = 9.