My Easy Science
Dose-Response and Emax Plotter
Drag EC50 and Hill and watch the curve move. Compare two drugs, a full agonist against a partial agonist, and see what an antagonist does.
Drag a slider, then tap Show effect and EC50.
For learning only. Not for patient care decisions. Always check with a qualified professional and the product label.
Results per drug
| Drug | EC10 | EC50 | EC90 | Emax | Potency ratio (vs A) | Steepness |
|---|---|---|---|---|---|---|
| Drug A | — | — | — | — | — | — |
| Drug B | — | — | — | — | — | — |
| Effect at typed conc. | — | — | — | |||
EC50 is the concentration that gives half the max effect. Lower EC50 means more potent.
Curve data
| Concentration | Effect, Drug A (%) |
|---|
Values from the drawn curve.
Starting values
Worked example: drug A is a full agonist, Emax 100%, EC50 10, Hill slope 1. Concentration to read: 10. At that concentration the effect is 50% — half the max, because the concentration equals the EC50.
How it works
Checked against three hand-worked examples (see the page source comments).
Results are shown to 2 decimal places, except Emax and E0, which are whole numbers, and effects, which are shown to 1 decimal place.
A dose-response curve has three numbers. Emax is the ceiling, the most effect the drug can ever give. EC50 is the concentration that gives half of that ceiling, so a smaller EC50 means a more potent drug. The Hill coefficient sets the steepness: 1 is the plain curve, 2 is steeper, and below 1 is shallower. At the EC50 the effect is exactly half of Emax, whatever the Hill number is. Take Emax 100, EC50 10 and Hill 1: at a concentration of 10 the effect is 50, at 90 it is 90, and at 1 it is 9.09. Make the Hill coefficient 2 and the same drug at a concentration of 20 gives 80, because the curve switches on faster.
A partial agonist never reaches the ceiling, even at huge concentrations: its intrinsic activity is below 1, so its effective Emax is a fraction of the full one. A competitive antagonist does not lower the ceiling at all; it moves the whole curve to the right, so more agonist is needed for the same effect. With an antagonist concentration of 20 and a KB of 10, the EC50 triples, from 10 to 30, a dose ratio of 3. A non-competitive antagonist is different again: it lowers Emax itself, and no amount of extra agonist can get the full effect back.
Potency and efficacy are not the same thing. Potency is where the curve sits (EC50); efficacy is how high it goes (Emax). Two drugs can share an EC50 and still differ completely if one is a partial agonist. Drag the dashed EC50 line on the graph itself to feel how potency moves the curve without touching its height.