Drybench Assay product page
Drybench Assay.
IC50 and EC50 calculator with confidence intervals
Paste a table of concentrations and responses, fit 4PL curves in batch and read C50s with confidence intervals and a method paragraph, in your browser.
2,083 of 200,000 characters
A long table (compound, concentration with its unit in the header, response) or a wide one (concentration, then one column per compound). Tab- or comma-separated.
Responses are
Choose the biological meaning of this assay. Curve direction does not decide the endpoint name.
Preloaded: the worked MTT example's three compounds as percent viability. Replace it with your own table.
Inhibition assays use IC50; activation or agonism assays use EC50; unspecified assays use C50. A rising or falling curve can have either biological meaning.
Answer
Compound A2.16 µMpIC50 5.666Four-parameter logistic fit
IC50 2.16 µM (1.81 µM to 2.59 µM) · Hill −1.28 · Top 98.23 · Bottom 3.038
Each point is one well or row as read; the curve is fitted to the points, not their means.
Data table
Data for Compound A Well Concentration (M) Response Fitted Residual Kept point 1 100 µM 4.15 3.729 0.421 yes point 2 33.3 µM 5.33 5.802 −0.472 yes point 3 11.1 µM 12.86 13.42 −0.557 yes point 4 3.7 µM 35.54 34.8 0.742 yes point 5 1.23 µM 74.63 67.01 7.62 yes point 6 412 nM 81.73 88.09 −6.36 yes point 7 137 nM 105.9 95.54 10.4 yes point 8 45.7 nM 86.47 97.56 −11.1 yes point 9 15.2 nM 107.7 98.07 9.64 yes point 10 5.08 nM 100.3 98.19 2.07 yes point 11 100 µM 3.3 3.729 −0.429 yes point 12 33.3 µM 6.35 5.802 0.548 yes point 13 11.1 µM 12.52 13.42 −0.897 yes point 14 3.7 µM 33.08 34.8 −1.72 yes point 15 1.23 µM 68.87 67.01 1.86 yes point 16 412 nM 83.77 88.09 −4.32 yes point 17 137 nM 99.84 95.54 4.3 yes point 18 45.7 nM 97.22 97.56 −0.341 yes point 19 15.2 nM 95.1 98.07 −2.97 yes point 20 5.08 nM 96.96 98.19 −1.23 yes point 21 100 µM 3.3 3.729 −0.429 yes point 22 33.3 µM 8.12 5.802 2.32 yes point 23 11.1 µM 13.45 13.42 0.0334 yes point 24 3.7 µM 32.58 34.8 −2.22 yes point 25 1.23 µM 65.4 67.01 −1.61 yes point 26 412 nM 86.81 88.09 −1.28 yes point 27 137 nM 88.93 95.54 −6.61 yes point 28 45.7 nM 102.2 97.56 4.65 yes point 29 15.2 nM 97.22 98.07 −0.849 yes point 30 5.08 nM 96.96 98.19 −1.23 yes Compound B184 nMpIC50 6.735Four-parameter logistic fit
IC50 184 nM (152 nM to 220 nM) · Hill −0.979 · Top 96.79 · Bottom 15.54
Each point is one well or row as read; the curve is fitted to the points, not their means.
Data table
Data for Compound B Well Concentration (M) Response Fitted Residual Kept point 1 100 µM 16.41 15.71 0.703 yes point 2 33.3 µM 18.02 16.03 1.99 yes point 3 11.1 µM 15.31 16.98 −1.67 yes point 4 3.7 µM 19.71 19.62 0.0929 yes point 5 1.23 µM 22.08 26.44 −4.36 yes point 6 412 nM 39.09 40.93 −1.84 yes point 7 137 nM 62.53 61.96 0.574 yes point 8 45.7 nM 73.44 80.23 −6.79 yes point 9 15.2 nM 98.32 90.27 8.05 yes point 10 5.08 nM 89.1 94.44 −5.34 yes point 11 100 µM 15.31 15.71 −0.397 yes point 12 33.3 µM 16.08 16.03 0.0466 yes point 13 11.1 µM 18.19 16.98 1.21 yes point 14 3.7 µM 21.66 19.62 2.04 yes point 15 1.23 µM 28.51 26.44 2.07 yes point 16 412 nM 42.9 40.93 1.97 yes point 17 137 nM 62.19 61.96 0.234 yes point 18 45.7 nM 80.89 80.23 0.659 yes point 19 15.2 nM 89.86 90.27 −0.406 yes point 20 5.08 nM 94.17 94.44 −0.271 yes point 21 100 µM 12.44 15.71 −3.27 yes point 22 33.3 µM 17.09 16.03 1.06 yes point 23 11.1 µM 18.02 16.98 1.04 yes point 24 3.7 µM 17.18 19.62 −2.44 yes point 25 1.23 µM 26.91 26.44 0.468 yes point 26 412 nM 43.15 40.93 2.22 yes point 27 137 nM 61.43 61.96 −0.526 yes point 28 45.7 nM 79.79 80.23 −0.441 yes point 29 15.2 nM 94.51 90.27 4.24 yes point 30 5.08 nM 93.5 94.44 −0.941 yes Compound Cnumerically unresolvedFour-parameter logistic fit
C50 beyond the highest concentration
Each point is one well or row as read; the curve is fitted to the points, not their means.
Data table
Data for Compound C Well Concentration (M) Response Fitted Residual Kept point 1 100 µM 37.65 – – yes point 2 33.3 µM 69.04 – – yes point 3 11.1 µM 78.01 – – yes point 4 3.7 µM 90.7 – – yes point 5 1.23 µM 96.12 – – yes point 6 412 nM 90.7 – – yes point 7 137 nM 100.5 – – yes point 8 45.7 nM 105.7 – – yes point 9 15.2 nM 99.33 – – yes point 10 5.08 nM 103.1 – – yes point 11 100 µM 43.41 – – yes point 12 33.3 µM 70.9 – – yes point 13 11.1 µM 88.08 – – yes point 14 3.7 µM 92.4 – – yes point 15 1.23 µM 99.33 – – yes point 16 412 nM 105.8 – – yes point 17 137 nM 92.9 – – yes point 18 45.7 nM 100.6 – – yes point 19 15.2 nM 109.5 – – yes point 20 5.08 nM 105.5 – – yes
95 percent profile extra-sum-of-squares interval on log10 IC50; a value the data cannot support is withheld with the reason.
Open in the appThe app carries no data in its link; paste your own export there.
Worked example
- The worked MTT example's three compounds are preloaded as percent viability; the first fits with a C50 near 2.2 µM and a 95 percent profile extra-sum-of-squares interval of about 1.8 to 2.6 µM; the third fit is numerically unresolved and its value is withheld with the reason.
- Paste your own long or wide table with the unit in the concentration header; a plate export needs the plate map, which the app has.
Method
- Four-parameter logistic fit. Hill AV. J Physiol 1910;40:iv-vii (the logistic form); Ritz C, Baty F, Streibig JC, Gerhard D. Dose-response analysis using R. PLoS ONE 2015;10:e0146021 (the LL.4 parameterisation the fixtures map to).Version 2 unweighted estimates and intervals are checked against the compatible R fixtures. Historical relative-loss and reporting-policy fixtures are archival, not validation of IRLS or the permutation gate.
- Bounded Levenberg-Marquardt with an analytic Jacobian and deterministic starts. Levenberg K. Q Appl Math 1944;2:164-168; Marquardt DW. J Soc Indust Appl Math 1963;11:431-441 (original papers).Version 2 unweighted estimates and intervals are checked against the compatible R fixtures. Historical relative-loss and reporting-policy fixtures are archival, not validation of IRLS or the permutation gate.
- Profile extra-sum-of-squares interval on log10 C50. The objective rises to its minimum × (1 + F(0.95; 1, n − p)/(n − p)) with the other parameters refitted (brief §4.1); the asymmetrical interval GraphPad's Prism 8 guide names as its initial default (read 5 October 2026); Only unweighted independent Gaussian errors with constant variance; nonlinear F approximation. A bound not reached within 10 log10 units or after an unresolved refit is labelled not bounded within the search, not mathematically infinite. Zero residual variance and relative-weighted fits have no interval.Unweighted profile extra-sum-of-squares computation checked against compatible R fixtures. Uses an approximate nonlinear F threshold; bounds beyond or unresolved within the search are not claimed mathematically infinite.
- Response evidence and reporting policy. A two-sided within-plate permutation test of dose-response rank covariance supplies response evidence at p < 0.05; independent exchangeable observations are required. Exact through n=8, otherwise 1999 fixed-seed permutations with plus-one p-value. This is this app’s reporting policy, not biological-activity proof. Sebaugh JL. Guidelines for accurate EC50/IC50 estimation. Pharm Stat 2011;10:128-134 (PMID 22328315; abstract read 6 October 2026): two concentrations beyond each bend point; bend points at IC50 × 4.6805^(±1/|Hill|) (Sebaugh and McCray 2003, value checked by arithmetic; paper not yet read).Version 2 uses a two-sided within-plate rank permutation test at 0.05 for response evidence, plus numerical, bracketing and plateau checks. Exchangeability is required; this app-specific reporting policy does not establish biological activity. Version 1 F-gate fixtures are archival.
Limits
- For research and education only, and not medical advice: a C50 estimated here describes this assay under these conditions and is not a binding constant.
- The reported C50 is always the four-parameter logistic fit, with any parameter fixable; no five-parameter dose-response fits (standard curves, ELISA among them, are fitted in the Standard curve analysis). A bell-shaped or biphasic curve can be fitted beside it for one curve, for information: it describes the curve's shape over the tested concentrations, does not show two binding sites, two targets or two mechanisms, does not say why the response turns, and reports no interval.
- The app refuses to fit fewer than four distinct concentrations, treats a concentration of zero as a control, and never extrapolates: a C50 the tested concentrations do not bracket is withheld with the reason.
- Confidence intervals are profile extra-sum-of-squares by default and Wald as the named alternative, both on log10 C50 and both assuming independent errors of constant variance; relative fits assume SD proportional to response and variance proportional to its square, and have no intervals; a bound not reached within ten log units is not bounded within the search.