Medical disclaimer: This calculator is for informational purposes only. It does not constitute medical advice. Always follow your dermatologist’s prescribed dosing schedule and consult them before making any changes to your treatment.
Accutane Cumulative Dose Calculator
💊 Accutane cumulative dose guidelines: Standard treatment target is 120-150 mg/kg total over 4-6 months. Higher doses (up to 180 mg/kg) may be used for severe or resistant acne.
⚠️ Medical disclaimer: This calculator provides estimates only. Actual dosing should be determined by a qualified dermatologist based on individual patient response, side effects, and lab monitoring.
How to Use This Calculator
The calculator needs two numbers: your body weight and your prescribed daily dose. That’s it.
Enter Your Weight and Daily Dose
Type your weight in kilograms or pounds (the calculator converts). Then enter the milligrams your dermatologist prescribed per day — check your prescription if you’re unsure. Common doses are 20 mg, 40 mg, 60 mg, and 80 mg.
Understanding Your Target Range (150–220 mg/kg)
The calculator shows your progress toward three milestones: 120 mg/kg (the old minimum), 150 mg/kg (the current lower bound), and 220 mg/kg (the upper bound associated with the lowest relapse rates in 2026 research).
Your dermatologist decides where in that range you should land. Most patients target somewhere between 150 and 220 mg/kg depending on acne severity, tolerance, and how your skin has responded. The calculator gives you the timeline for all three targets so you can have an informed conversation about your treatment length.
Low-Dose vs. Standard-Dose Mode
Toggle the low-dose switch if you’re on a microdose or low-dose protocol (typically 10–30 mg/day). The cumulative dose math is identical — you’re reaching the same target, just more slowly. A 70 kg patient on 20 mg/day takes roughly 17–18 months to hit 150 mg/kg versus 8–9 months at 40 mg/day.
What Is Accutane Cumulative Dose?
Cumulative dose is the total amount of isotretinoin you take over your entire course, measured in milligrams per kilogram of body weight (mg/kg). It’s not the same as your daily dose — it’s the running total.
Why Cumulative Dose Matters More Than Daily Dose
Here’s something most patients don’t realize until they’re months into treatment: whether you take a higher dose for fewer months or a lower dose for more months, what actually determines your outcome is the total cumulative dose you reach.
A 2024 systematic review published in JEADV Clinical Practice analyzed dosing across multiple studies and found that cumulative dose was the strongest predictor of relapse — not the daily dose used, not the speed of treatment. Two patients who both reach 150 mg/kg have similar outcomes regardless of whether they got there in 5 months or 14.
This matters for low-dose patients especially. There’s a persistent myth that low-dose Accutane doesn’t work as well. It does — as long as you reach the target.
The 2026 Updated Guideline: 150–220 mg/kg
The figure you’ll see most often online is 120–150 mg/kg. That’s based on older research, and a lot of calculators — including some well-known ones — still use 135 mg/kg as the mean target.
In 2026, Lai and Barbieri published a study in JAMA Dermatology that changed the picture. Patients who reached cumulative doses of 220 mg/kg or more had a relapse rate of 26.9%. Those who didn’t reach 220 mg/kg had a relapse rate of 47.4% — nearly double.
The researchers also found that each additional mg/kg of cumulative dose was associated with a 0.4% reduction in relapse risk and a 1% reduction in retreatment risk. That adds up. A patient who reaches 220 mg/kg instead of 150 mg/kg carries meaningfully lower long-term risk.
The current evidence-based target range is 150–220 mg/kg. The calculator reflects this.
How to Calculate Accutane Cumulative Dose
You can calculate cumulative dose manually if you want to double-check the calculator’s math.
The Cumulative Dose Formula
Cumulative dose (mg/kg) = Total milligrams taken ÷ Body weight (kg)Example: A 70 kg patient who has taken 7,000 mg total has a cumulative dose of 100 mg/kg (7,000 ÷ 70 = 100).
To calculate how many total milligrams you need to reach a target:
Total mg needed = Target mg/kg × Body weight (kg)Example: A 70 kg patient targeting 150 mg/kg needs 10,500 mg total (150 × 70 = 10,500).
At 40 mg/day, that’s 262.5 days — about 8.75 months. At 60 mg/day, it’s 175 days — about 5.8 months.
Accutane Dosage Chart by Weight
The table below shows total milligrams needed to reach key cumulative dose targets, and estimated treatment duration at three common daily doses.
| Weight | 150 mg/kg target | At 40 mg/day | At 60 mg/day | At 80 mg/day |
|---|---|---|---|---|
| 50 kg | 7,500 mg | 6.3 months | 4.2 months | 3.1 months |
| 60 kg | 9,000 mg | 7.5 months | 5.0 months | 3.75 months |
| 70 kg | 10,500 mg | 8.8 months | 5.8 months | 4.4 months |
| 80 kg | 12,000 mg | 10.0 months | 6.7 months | 5.0 months |
| 90 kg | 13,500 mg | 11.3 months | 7.5 months | 5.6 months |
| 100 kg | 15,000 mg | 12.5 months | 8.3 months | 6.3 months |
For 220 mg/kg target, multiply each “total mg” figure by 1.47. Treatment durations scale accordingly.
These are estimates. Your dermatologist may adjust your dose during treatment, which shifts the timeline.
How Long Will You Be on Accutane?
Standard Accutane courses last 4–6 months. But that range assumes you’re on a moderate-to-high daily dose and targeting the 120–150 mg/kg benchmark. The actual answer depends on your weight, your prescribed dose, and where in the 150–220 mg/kg range your dermatologist is aiming.
Standard Dose Timeline (0.5–1 mg/kg/day)
At 0.5 mg/kg/day, a 70 kg patient takes 35 mg daily (rounded to 40 mg in practice). To reach 150 mg/kg takes about 8–9 months. To reach 220 mg/kg takes about 12–13 months.
At 1 mg/kg/day, the same patient takes 70 mg daily. To reach 150 mg/kg takes about 5 months. To reach 220 mg/kg takes about 7 months.
Most dermatologists start patients at 0.5 mg/kg/day for the first month to assess tolerance, then increase. That initial lower dose period is included in the calculator’s estimate.
Low-Dose and Microdose Accutane Timeline
Low-dose protocols (0.25–0.4 mg/kg/day) use 10–30 mg daily for most patients. The benefit is fewer side effects — less dryness, less liver stress, more tolerable for people who struggle with standard dosing. The tradeoff is time.
A 70 kg patient on 20 mg/day takes 525 days to reach 150 mg/kg — about 17.5 months. At 30 mg/day, it’s about 11.7 months. The calculator shows you the exact timeline for your dose.
Accutane Relapse Risk and Cumulative Dose
The whole point of tracking cumulative dose is reducing the chance your acne comes back. Here’s what the data actually shows.
What Happens If You Don’t Reach the Target Dose?
Patients who stop before reaching an adequate cumulative dose are significantly more likely to need a second course. In the 2026 JAMA Dermatology study, those who stopped under 220 mg/kg had a nearly 50% chance of relapse within a few years of stopping.
A second course of Accutane is possible, but it’s not ideal. It restarts the iPledge monitoring requirements, the blood work schedule, the side effect exposure. Getting there the first time — reaching an adequate cumulative dose — is the better outcome.
How Higher Cumulative Doses Reduce Relapse Risk
The relationship between cumulative dose and relapse risk isn’t a cliff — it’s a slope. Every additional mg/kg you accumulate reduces your relapse probability. The drop-off is most significant as you move from 120 to 150 mg/kg, and meaningful improvement continues through 220 mg/kg.
This is why some dermatologists now target 180–220 mg/kg for patients with severe or treatment-resistant acne: the additional months of treatment are worth the reduction in long-term recurrence risk.
Frequently Asked Questions
What is the maximum cumulative dose of isotretinoin?
There’s no formal maximum, but the evidence supports targeting up to 220 mg/kg. The 2026 JAMA Dermatology study found patients who reached 220 mg/kg had a 26.9% relapse rate — roughly half the rate seen in patients who stopped earlier. Higher cumulative doses appear to continue reducing relapse risk, though data beyond 220 mg/kg is limited.
How much Accutane do I need for my weight?
Your total Accutane need is your target cumulative dose (in mg/kg) multiplied by your weight in kilograms. For a 70 kg person targeting 150 mg/kg, that’s 10,500 mg total. At 40 mg/day, it takes about 262 days (8.8 months). The dosage chart above covers common weights; the calculator handles your exact numbers.
Is the 120–150 mg/kg isotretinoin guideline still current?
Not fully. The 120–150 mg/kg figure came from older research and was adopted as a clinical rule of thumb. Newer data — particularly the 2026 Lai and Barbieri study in JAMA Dermatology — supports extending treatment to 150–220 mg/kg for lower relapse rates. Some older calculators and references still use 135 mg/kg as the mean target, which is now considered conservative.
What is the highest dose of Accutane?
Standard daily dosing runs 0.5–1 mg/kg/day. Some protocols go up to 2 mg/kg/day for severe nodular acne, though side effects increase at higher doses. The cumulative dose target of up to 220 mg/kg is supported by current evidence. Your dermatologist determines what’s appropriate for your case.
Can I use this calculator for low-dose Accutane?
Yes. Enter your actual daily dose — even 10 mg or 20 mg — and your weight. The calculator shows your timeline to each cumulative dose milestone. Low-dose and microdose protocols reach the same targets, just over a longer period.