Calculator Inputs
The page uses a single stacked layout overall, while the calculator fields use three columns on large screens, two on medium screens, and one on mobile.
Example Data Table
These sample rows show how different rates and dilution settings change the estimated substrate concentration.
| Scenario | Observed Rate | Blank Rate | Vmax | Km | Dilution Factor | Estimated Assay Substrate | Estimated Original Substrate |
|---|---|---|---|---|---|---|---|
| Assay A | 42 | 2 | 120 | 5 | 4 | 2.5000 mM | 10.0000 mM |
| Assay B | 68 | 3 | 150 | 8 | 1.5 | 5.2000 mM | 7.8000 mM |
| Assay C | 24 | 1 | 90 | 3 | 10 | 1.1030 mM | 11.0300 mM |
Formula Used
The calculator rearranges the Michaelis-Menten equation to solve for substrate concentration from a measured reaction rate.
Notes:
- Observed rate must be lower than Vmax after corrections.
- Km and the solved concentration stay in the same concentration unit.
- Blank subtraction helps remove baseline instrument or reagent signal.
- The uncertainty range uses your entered rate uncertainty percentage.
How to Use This Calculator
- Enter the measured reaction rate from your enzyme assay.
- Add the blank rate to remove background signal.
- Provide Vmax and Km from literature or calibration work.
- Enter the dilution factor applied before the assay.
- Use the inhibition adjustment factor if inhibitors reduced the apparent rate.
- Set assay volume and sample aliquot volume for source concentration estimates.
- Add stock concentration and desired working volume for preparation guidance.
- Press the calculate button to show results above the form.
- Download the results as CSV or PDF if needed.
Frequently Asked Questions
1. What does this calculator estimate?
It estimates substrate concentration from enzyme kinetics data by rearranging the Michaelis-Menten equation. It also reports corrected rates, dilution-adjusted values, uncertainty ranges, and preparation volumes.
2. Why must the adjusted rate stay below Vmax?
The rearranged equation divides by Vmax minus rate. If rate equals or exceeds Vmax, the denominator becomes zero or negative, making the concentration physically invalid for this model.
3. What is the purpose of blank rate correction?
Blank correction removes background absorbance, fluorescence, or reagent drift. That gives a truer enzymatic rate and improves the substrate concentration estimate.
4. When should I use the dilution factor?
Use it when the original sample was diluted before measurement. The calculator multiplies the solved assay concentration by that factor to recover the estimated original concentration.
5. What does the inhibition adjustment factor do?
It scales the corrected rate before solving for concentration. This is useful when you want a simple correction for rate suppression caused by inhibitors or challenging assay matrices.
6. Can I change the concentration unit?
Yes. The unit selector changes labels throughout the results. Keep Km, stock concentration, and intended interpretation consistent in the same chosen concentration unit.
7. What does the uncertainty range mean?
The calculator perturbs the adjusted rate by your uncertainty percentage and solves two additional concentrations. That creates a practical low and high estimate range.
8. Why is a preparation volume included?
After solving the assay concentration, many labs need a matching working solution. The preparation section estimates how much stock and buffer are needed for that target volume.