Catalyst Turnover Frequency Calculator

Enter Catalyst Data

Use either the direct product method or the flow-and-conversion method. You can also enter total active sites directly or derive them from catalyst mass and site density.

Calculation method

Active-site basis

Temperature

Pressure

Product amount

Used for the direct product method.

Reaction time

Used for the direct product method.

Limiting reactant feed flow

Used for the flow-and-conversion method.

Conversion (%)

Selectivity to product (%)

Stoichiometric factor

Moles of product per mole of reactant consumed.

Run duration

Used for TON in the flow-and-conversion method.

Correction factor (%)

Use this for assay, collection, or purity correction.

Total active sites

Used when active sites are entered directly.

Catalyst mass

Required when using site density.

Site density

Used with catalyst mass to derive active sites.

Run notes

Clear

Formula Used

Turnover Frequency:

TOF = Product formation rate / Moles of active catalytic sites

Typical units: s^-1, min^-1, or h^-1

Direct product method:

Product rate = Corrected product amount / Reaction time

Flow and conversion method:

Product rate = Feed flow × Conversion × Selectivity × Stoichiometric factor × Correction factor

Turnover Number over run:

TON = Total product formed during the run / Moles of active catalytic sites

The most important source of uncertainty is often the active-site count. TOF values should only be compared when site-counting assumptions and operating conditions are aligned.

How to Use This Calculator

Choose your calculation method. Use direct product mode for batch data or flow-and-conversion mode for continuous or feed-based experiments.
Enter product, flow, conversion, selectivity, and stoichiometric information in the units that match your laboratory record.
Choose how to define active sites. Enter total active sites directly or derive them from catalyst mass and site density.
Apply a correction factor if your measured amount needs purity, assay, recovery, or collection adjustment.
Submit the form to show the result block under the header and above the calculator form.
Use the CSV and PDF buttons to export the displayed result summary for reporting or benchmarking.

Example Data Table

Parameter	Example Value
Calculation method	Flow and conversion
Limiting reactant feed flow	120 mmol/h
Conversion	45%
Selectivity	92%
Stoichiometric factor	1.00
Run duration	4 h
Catalyst mass	0.25 g
Site density	1.4 mmol/g
Calculated active sites	0.35 mmol
Product rate	49.68 mmol/h
TOF	0.03943 s^-1 or 141.94 h^-1
TON over run	567.77

Frequently Asked Questions

1. What does turnover frequency measure?

Turnover frequency measures how many product molecules each active catalytic site generates per unit time. It is a normalized rate, not a total yield.

2. What is the difference between TOF and TON?

TOF is a time-based activity metric. TON is cumulative and shows how many turnovers each active site completed over the whole run.

3. Why does the active-site count matter so much?

TOF changes directly with the site count. If you underestimate active sites, TOF looks artificially high. If you overestimate them, TOF looks artificially low.

4. Should I use total metal loading as active sites?

Only when that assumption is justified. Many systems have inaccessible, inactive, or blocked metal atoms. Site density from chemisorption or titration is usually stronger.

5. When should I use the direct product method?

Use it for batch reactions or experiments where you know the collected product amount and elapsed reaction time more reliably than feed conversion.

6. When should I use the flow-and-conversion method?

Use it for continuous experiments, steady-state reactor studies, or any setup where feed flow, conversion, and selectivity are your primary measurements.

7. Why is selectivity included in the flow method?

Conversion alone measures reactant disappearance. Selectivity adjusts that value to the specific desired product, which is necessary for product-based TOF.

8. Can I compare TOF values from different papers directly?

Compare them carefully. Matching temperature, pressure, reactor regime, conversion range, site definition, and normalization method is essential for a fair comparison.