XLfit is a Microsoft Excel add-in that can perform regression analysis, curve fitting, and statistical analysis. It is approved by the UK National Physical Laboratory and the US National Institute of Standards and Technology^[1] XLfit can generate 2D and 3D graphs and analyze data sets. XLfit can also analyse the statistical data. It includes over seventy linear and non-linear curve fitting models.^[2] Predefined categories include:

• Exponential/Log, Power Series, Sigmoidal, Hyperbolic, Yield Density, Linear, Polynomial, Dose Response, Pharmacology, Equilibrium and Inhibition.
• Levenberg-Marquardt fitting algorithm.

A range of statistical calculations can also be applied to the data from within the spreadsheet. Example statistics include:^{[further explanation needed]}

• F-test and t-test
• Area under the curve / ROC
• Confidence intervals
• Error values relating to parameter values or any point on the curve.

Available statistical models include Spearman's rank correlations, Student's t-test, Mann–Whitney U test, least squares, and ANOVA, among others.^{[citation needed]} A model editor also allows users to add their own models and statistics to the ones provided.