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Free IC50 Calculator and Dose Response Curve Generator

Fit concentration-response measurements with a 3PL or 4PL model. Read the relative IC50 or EC50 and export the points with the fitted curve.

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Free IC50 Calculator and Dose Response Curve Generator— templates & examples

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Dose response curve tools

Free IC50 Calculator and Dose Response Curve Generator

Fit your measured responses and show the midpoint, plateaus and curve together.

An IC50 calculator fits a dose response curve to estimate the concentration halfway between its response plateaus. Enter concentration and response measurements to fit an increasing or decreasing dose response curve. Compare 3PL and 4PL fits, read the relative IC50 or EC50, and export the plotted measurements with the fitted line.

Create a dose response curve
IC50 dose-response example with decreasing observations and a fitted 4PL curve on a concentration axis in nM
  • Enter at least five distinct concentrations
  • Use four fitted parameters in 4PL
  • Identify the fitted midpoint
  • Export SVG or PNG

Dose Response Curve Features

SciFig’s IC50 calculator fits measured concentration-response points and shows the curve alongside its parameters.

Fit concentration and response measurements

Paste numerical concentration and response values into SciFig’s IC50 calculator. The local fit uses your measurements to draw the points and dose response curve together. Distinct concentrations establish the x positions, while repeat measurements show observations at the same dose. Keep the concentration unit with the figure so that the midpoint has an explicit scale.

  • Enter at least five distinct concentrations
  • Include repeat measurements
  • Keep concentration units visible
Fit a dose response curve

Choose a 3PL or 4PL model

Select the model that matches the comparison you want to make. SciFig’s 4PL curve fitting estimates the lower plateau, upper plateau, midpoint and Hill slope. Its 3PL option fixes the Hill slope at one. Displaying the model beside the result makes that choice part of the figure rather than a hidden calculation.

  • Use four fitted parameters in 4PL
  • Fix Hill slope to one in 3PL
  • Compare the model with the points
Choose a fitting model

Read a relative IC50 or EC50

The reported midpoint is the concentration halfway between the fitted plateaus. A decreasing response can express inhibition as a relative IC50; an increasing response can express stimulation as an EC50. The midpoint is not necessarily the concentration at a raw response value of fifty, so the fitted bounds remain useful context.

  • Identify the fitted midpoint
  • Retain increasing or decreasing direction
  • Show the response plateaus
Calculate the relative midpoint

Export the points and fitted line

Download a dose response figure as SVG or PNG with the concentration axis, response values and fitted curve together. Use the plot in an assay discussion or presentation while keeping the input data available for another fit. A log concentration view emphasizes relative dose spacing; a linear view also accommodates zero-concentration observations.

  • Export SVG or PNG
  • Set the concentration unit
  • Choose an appropriate axis view
Export the fitted curve

How to Create the Figure

Use the IC50 calculator to enter measurements, choose the fitting model and export the curve.

  1. Enter concentration-response pairs

    Paste your measurements with numerical concentrations and responses. Include at least five distinct nonnegative concentration values and keep repeated measurements as separate observations. Set a concentration unit that matches your experiment so that the fitted midpoint is expressed on the same scale.

  2. Choose the fitting model

    Select 3PL or 4PL. The fit estimates whether the measured response increases or decreases. SciFig’s 3PL fixes Hill slope to one; 4PL estimates the slope. These choices define the curve fitted to the observations rather than changing the measured response values.

  3. Fit and read the parameters

    Run the fit to see the curve, data points and estimated parameters. Read the midpoint together with the fitted lower and upper plateaus. Constant responses, insufficient concentrations and nonconvergent fits produce a visible error instead of a fabricated midpoint.

  4. Set units and export the figure

    Set the concentration unit and axis view, then download SVG or PNG. Keep the data table with the figure to support later comparisons. The relative IC50 or EC50 uses the concentration unit entered with the observations.

Dose Response Curve Uses

Use the dose response curve generator to present concentration-response measurements in assay discussions and teaching material.

IC50 dose-response example with decreasing observations and a fitted 4PL curve on a concentration axis in nM

Summarize an inhibition experiment

An assay discussion often needs both the measured responses and the fitted inhibition curve. Enter the concentration series, fit a decreasing model and export a figure with its relative IC50. Keeping the plateaus visible explains which response range defines the halfway point.

Explore this example
EC50 example with increasing response observations and a fitted 4PL curve

Show an increasing response

Use an increasing curve when the measured response rises with concentration. The fitted EC50 marks the midpoint between the model’s plateaus. Place the exported figure alongside the experiment description so the response direction and concentration unit are explicit to the reader.

Explore this example
IC50 curve fitted to replicate observations at each concentration

Discuss repeated measurements

Repeat observations at a concentration provide context for the fitted line. Keep those measurements in the input rather than replacing the whole series with an illustrative curve. The plotted points let a laboratory meeting discuss the observed pattern alongside the model result.

Explore this example
Relative IC50 dose-response example with two nonzero fitted plateaus

Explain relative and absolute midpoint

Teaching material can use a curve whose lower plateau is above zero. Show that a relative IC50 is halfway between the fitted bounds, rather than automatically at a response of fifty. The labeled plot connects the definition to a concrete curve shape.

Explore this example
Decreasing IC50 dose-response observations with a fitted 4PL curve

Compare model assumptions

A methods presentation can compare 4PL curve fitting with SciFig’s 3PL model, which fixes the Hill slope at one. Use the same measurements for both fits and retain the model label with each export. The figures communicate what changed in the calculation.

Explore this example
IC50 dose-response example with decreasing observations and a fitted 4PL curve on a concentration axis in nM

Prepare a pharmacology figure

Export a concentration-response plot for an experiment summary or presentation. Retain axis labels and units with the data points so the curve can be read independently. For a wider figure set built from your measurements, continue with SciFig DataChart (charts and graphs from your data).

Explore this example

How Researchers Use SciFig

I brought a concentration series and repeated response measurements to our assay meeting. The IC50 calculator put the observations beside the fitted curve and its plateaus. Reading the relative midpoint with those bounds made it easier to explain exactly which response range our comparison referred to in the exported figure.

Marta V.

Pharmacology doctoral researcher, University of Barcelona

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