Interactive Calculator
Antipsychotic dose conversion is a practical way to estimate how one medication compares to another in terms of approximate antipsychotic potency. This page uses chlorpromazine equivalents (CPZ equivalents) as a common reference point, then converts from that reference to your selected target medication.
What this calculator does
The calculator performs a two-step process:
- Converts the source dose into an estimated chlorpromazine equivalent dose.
- Converts the chlorpromazine equivalent into an estimated dose of the target antipsychotic.
This approach is widely used in research and in rough planning discussions, but it is not a substitute for individualized prescribing.
How to use it
- Select the patient’s current antipsychotic.
- Enter the current oral total daily dose in milligrams.
- Select the target antipsychotic.
- Click Calculate Equivalent Dose.
The result includes both an estimated CPZ equivalent and an estimated target dose, plus a ±20% range to highlight uncertainty.
Approximate reference values used in this tool
The table below shows the internal assumptions: the dose (mg/day) that is treated as roughly equivalent to 100 mg/day chlorpromazine.
| Medication | Approx. mg/day ≈ 100 mg CPZ |
|---|---|
| Chlorpromazine | 100 mg |
| Haloperidol | 2 mg |
| Fluphenazine | 2 mg |
| Perphenazine | 8 mg |
| Risperidone | 2 mg |
| Paliperidone | 3 mg |
| Olanzapine | 5 mg |
| Quetiapine | 75 mg |
| Aripiprazole | 7.5 mg |
| Ziprasidone | 40 mg |
| Lurasidone | 20 mg |
| Clozapine | 50 mg |
| Amisulpride | 100 mg |
Important caveats before any clinical use
1) Equivalence is an estimate, not an exact biological match
Two doses may look “equivalent” by CPZ calculations but still differ in sedation, prolactin effect, extrapyramidal symptoms, metabolic burden, and receptor profile.
2) Switching plans matter as much as equivalent dose
Direct switch, overlap, or gradual cross-taper can each produce different outcomes. Withdrawal effects and rebound symptoms can occur even when a mathematically equivalent target dose is chosen.
3) Context changes the interpretation
- Acute agitation vs maintenance treatment goals
- First-episode psychosis sensitivity to side effects
- Comorbid substance use or medical illness
- Age, liver/kidney function, and polypharmacy interactions
4) LAI formulations are not directly converted here
This calculator is built for oral daily dose estimates. Depot/LAI conversion requires product-specific loading schedules and pharmacokinetic guidance.
Worked example
If someone is taking 4 mg/day risperidone:
- Risperidone 2 mg ≈ 100 mg CPZ
- So 4 mg/day risperidone ≈ 200 mg/day CPZ
- Olanzapine 5 mg ≈ 100 mg CPZ, therefore 200 mg CPZ ≈ 10 mg/day olanzapine
This is only a starting estimate. Final treatment decisions should account for clinical response and tolerability over time.
FAQ
Can I use this to change my own medication?
No. This is not personal medical advice. Medication changes should be made only with a licensed prescriber.
Why include a ±20% range?
Because published equivalence estimates differ across studies, populations, and methods. The range reflects uncertainty and encourages cautious interpretation.
Is a higher CPZ equivalent always “better”?
No. Higher dose does not necessarily mean better outcomes and may increase adverse effects. The goal is effective symptom control at the lowest appropriate dose.
Method note
The conversion model in this page is a simplified educational framework based on commonly cited chlorpromazine-equivalent anchors in psychiatric literature. Real-world prescribing should follow up-to-date guidelines, product labels, and specialist judgment.