Significant figures & error bars
A measurement is a range, not a number. These tools carry the range through your calculation and tell you whether your conclusion holds across all of it, or only at the middle.
Significant figures
Carry uncertainty through a formula
Example loaded: g from a pendulum, length L in metres and period T in seconds. Type your own formula and the variable table rebuilds itself.
How the range is found
Worst-case range: the formula is evaluated at every combination of each variable's low and high value (and, for up to three variables, across a fine grid in between), and the smallest and largest results are reported. This is the honest "could it be anywhere in here?" range most packets ask for.
Standard propagation: the usual first-order formula, √Σ(∂f/∂x · Δx)², which assumes independent errors and gives a smaller, typical spread.