● your data — fitted Michaelis-Menten curve. Dashed lines mark Vmax and Km (where v = ½Vmax).
How to find Km and Vmax from data
Raw enzyme data is a curve, which is hard to fit by eye — so the classic trick is to linearize it. Taking reciprocals of the Michaelis-Menten equation gives 1/v = (Km/Vmax)(1/[S]) + 1/Vmax, which is a straight line (the Lineweaver-Burk plot). Fit a line to your reciprocal points: the y-intercept is 1/Vmax, so Vmax = 1/intercept, and the slope is Km/Vmax, so Km = slope × Vmax. This tool does that regression for you and draws the resulting curve back over your original data so you can see how well it fits.
Method note: this uses the Lineweaver-Burk (double-reciprocal) linear fit, which is the standard textbook approach and shows its work clearly. It weights low-[S] points more heavily; for a publication you would use nonlinear regression, but for coursework and checking a lab this matches what you're taught.
Related tools: Enzyme kinetics simulator · all biochem tools.