Acne
Accutane (Isotretinoin) Cumulative Dose Calculator
This calculator is an educational estimation tool for the cumulative-dose math that physicians use to plan isotretinoin courses. It doesn't tell you what to take; only a licensed physician determines actual dosing.
Educational estimate only. This tool shows you how the cumulative dose for isotretinoin is calculated. The results are just estimates, not medical advice. Dosing determined by a licensed physician. Isotretinoin can cause severe birth defects; treatment requires pregnancy prevention and iPLEDGE enrollment, managed by your physician.
Common daily doses fall in the 30-80 mg range; your prescription is set by your physician.
Assumes 30 days per month.
Classic convention 120-150 mg/kg; newer research supports benefit toward ~220.
- mg/kg
Above ~220 mg/kg, the largest recent study found no additional relapse benefit - actual dosing is always physician-determined.
There is no universally agreed-upon target.
Traditionally, the standard 120-150 mg/kg was used; however, recent studies have shown lower relapse risks up to 220 mg/kg, with added benefits leveling off beyond that range. Some clinicians focus on the skin's response itself: 1-2 months of clear skin before stopping.
Your physician plans treatment based on your response, tolerability, and goals.
Wondering how long an Accutane course takes? The second mode estimates treatment length from your target.
What Is a Cumulative Dose?
Cumulative dose is the total amount of Accutane (isotretinoin) taken over the entire course of treatment in mg/kg, based on body weight. The two core factors that drive every isotretinoin treatment plan are dose (how much) and time (how long), both influencing this one number.
Cumulative dose is so important because it's a major factor in whether patients relapse or not. Higher ends of the cumulative dosage tend to experience lower relapse rates. It also gives you an idea of how long you'll be taking the medication, and how much you'll need daily.
Paichitrojjana et al. (2023). Drug Design, Development and Therapy
This is also why the specific capsule dose daily works differently for different people. A low dose for one person might be a high dose for another. It's less about whether you're taking 10, 20, or 40 mg specifically and more about the target cumulative dose based on your personal body weight and time frame.
How Is Cumulative Dose Calculated?
To calculate the cumulative dose, multiply the daily dose by the number of days on treatment, then divide by body weight in kilograms (remember to convert).
If your regimen isn't daily, divide the total by the number of days it spans.
If your dose changes during the course, you can calculate each phase separately and then add them up, which is what our calculator's "add phases" option does.
cumulative dose (mg/kg) = daily dose (mg) × days ÷ weight (kg)
Example: 40 mg/day for 6 months (~180 days) at 70 kg
40 × 180 = 7,200
7,200 ÷ 70 = ~103 mg/kg
The calculator gives you two options. "What cumulative dose will I reach?"does the math forward, taking a weight, dose, and course length to see the cumulative dose."How long to reach a target?" takes it backwards: given a weight, daily dose, and target, it estimates the months of treatment for the chosen target. Everything updates locally as you type; nothing is stored or sent anywhere.
The 120-150 mg/kg Target - and What Newer Research Says
The traditional 120 mg/kg target comes from research that showed doses below that range predicted relapse. The US standard that followed pairs 0.5-1 mg/kg/day dosing with a cumulative target of 120-150 mg/kg, and it remains the commonly cited convention in recent reviews.
Layton et al. (1993). British Journal of Dermatology
Paichitrojjana et al. (2023). Drug Design, Development and Therapy
A 2025 study changed things, though: across 20,000 patients, 22.5% relapsed, and cumulative doses all the way up to 220 mg/kg showed small additional reductions in relapse risk, plateauing above that range. The study does have limitations: it defined relapse as a new systemic acne prescription and estimated patient weight from averages and not measurements.
Lai & Barbieri (2025). JAMA Dermatology
Others argue that the total itself matters less than the individual's skin results. For example, some research found that neither daily nor cumulative dose changed relapse results as long as the patient continued treatment for at least two months after achieving clear skin.
The AAD guidelines don't recommend a specific cumulative-dose target.
Rademaker (2016). International Journal of Dermatology
Reynolds et al. (2024). Journal of the American Academy of Dermatology
What the 2025 study also found: daily dose didn't change long-term outcomes once the cumulative target was reached.
Standard and low-dose regimens reach the same cumulative target on different timelines - we break down the differences in the dosage guide →
What Affects Your Actual Dose
The calculator only does arithmetic. Your actual plan accounts for tolerability, bloodwork, response, and clinical judgment, which is why two people with identical numbers can be prescribed differently.
Reynolds et al. (2024). Journal of the American Academy of Dermatology
When to Talk to Your Provider
- Your estimate is far away from what you expected based on your prescription.
- You are on a low-dose or extended plan (timelines and totals read differently).
- You are experiencing side effects that feel beyond normal adjustment.
- You are early or mid-course and unsure how your progress compares.
Common Questions
What Is a Good Cumulative Dose for Accutane?
There is no universal, single agreed-upon number, but conventional guidelines target 120-150 mg/kg over an entire course. A large 2025 study found that the relapse risk continues to drop up to 220 mg/kg, with no added benefit beyond that. Some providers choose to treat until the skin is fully clear plus 1-2 months. Ultimately, your physician decides.
How Is Cumulative Dose Calculated?
Cumulative dose is the total amount of isotretinoin taken across the entire course, normalized to body weight: daily dose (mg) multiplied by days of treatment, divided by weight in kilograms. For example, 40 mg/day for 6 months (~180 days) at 70 kg is roughly 103 mg/kg. If your dose changes mid-course, each phase is calculated separately and summed.
Is 150 mg/kg Enough for Accutane?
Yes, conventional standards put 150 mg/kg near the top of the target range. Newer data from a 2025 study of around 20,000 patients found that relapse risk continues to drop up to roughly 220 mg/kg before plateauing. Whether you stop at 150 or continue is based on your response, tolerability, goals, and history, ultimately up to your physician.
Does a Higher Cumulative Dose Mean Fewer Relapses?
Yes, to a point. Higher cumulative doses are associated with lower relapse rates, and a recent study found the benefit continues up to 220 mg/kg, then plateaus with no additional benefit beyond that range. It's an association and not a personal guarantee, and taking more medication might also mean more side-effect burden. The decision is ultimately up to your physician.
What Happens if Cumulative Dose Is Too Low?
Relapse becomes more likely if the cumulative dose is too low. Research shows relapse rates between 20-40% overall, 22.5% in the latest larger-scale study. Cumulative doses below 120 mg/kg historically predict higher relapse rates. Young patients and those with more severe acne are more likely to relapse and may require a second course.
What Happens if I Miss Doses?
A missed dose doesn't erase progress - your cumulative total reflects what you've actually taken. Gaps simply extend the time to reach your target. Discuss any missed doses with your physician.
Can I Use This Calculator for Isotretinoin, Claravis, or Absorica?
Yes. Accutane, Claravis, Absorica, Amnesteem, and generic isotretinoin are all the same molecule: isotretinoin, so the cumulative-dose math is identical. Brands can differ in formulation and absorption details, which may matter clinically and are up to your physician to decide, not a calculator.
Why Does My Dermatologist's Target Differ From This Calculator?
Because the research itself has more than one camp: the classic 120-150 mg/kg convention, newer data supporting continued benefit toward ~220 mg/kg, and clinicians who treat to clearance plus 1-2 months rather than any fixed number, your physician is also weighing your response, side effects, and history. When their plan differs from a calculator, listen to your physician.
Sources
Primary evidence
- Individual studyLai & Barbieri (2025). Acne Relapse and Isotretinoin Retrial in Patients With Acne · JAMA Dermatology (Q1)
- Individual studyLayton et al. (1993). Isotretinoin for acne vulgaris - 10 years later; a safe and successful treatment · British Journal of Dermatology (Q1)
Expert context
- Clinical guidelineReynolds et al. (2024). Guidelines of care for the management of acne vulgaris · Journal of the American Academy of Dermatology (Q1)
- Narrative reviewPaichitrojjana et al. (2023). Oral Isotretinoin and Its Uses in Dermatology: A Review · Drug Design, Development and Therapy (Q1)
- Narrative reviewRademaker (2016). Making sense of the effects of the cumulative dose of isotretinoin in acne vulgaris · International Journal of Dermatology (Q1)
See whether treatment with a licensed provider may be appropriate for you
Interested in learning more about the results timeline, side effects, or iPLEDGE? Start with the complete isotretinoin (Accutane) guide, including its dosage section.