FDA dosing reference for Adderall IR & XR — plus ADHD medication conversion
Adderall (mixed amphetamine salts) is one of the most widely prescribed medications in the United States, used primarily for the treatment of Attention-Deficit/Hyperactivity Disorder (ADHD) and narcolepsy. It is available in two formulations: Adderall IR (Immediate Release), which provides 4–6 hours of effect, and Adderall XR (Extended Release), which provides 8–10 hours of coverage. Despite its widespread use, many patients and caregivers struggle to understand exactly what the recommended starting dose is, how doses are supposed to increase over time, and how Adderall compares to other ADHD medications they may be considering. This free Adderall Dosage Calculator provides a quick, structured reference to FDA-approved dosing information organized by age group (young children 3–5, children 6–12, adolescents 13–17, and adults 18+) and by condition (ADHD or narcolepsy). You can look up the recommended starting dose, the typical therapeutic dose range, the FDA-approved maximum dose, and the standard titration (dose increase) schedule for both Adderall IR and Adderall XR — all in one place. In addition to the dosage guide, the calculator includes a Medication Converter mode. This allows you to enter a current Adderall dose and see the approximate equivalent dose in other common ADHD medications, including Vyvanse (lisdexamfetamine), Ritalin (methylphenidate), Concerta (methylphenidate ER), Dexedrine (dextroamphetamine), and Focalin (dexmethylphenidate). These conversions are based on published clinical equivalency ratios — a 1:2 amphetamine-to-methylphenidate ratio is the most widely cited — as well as the well-known NeuroLaunch equivalency table used by clinicians. For children and adolescents, weight-based dosing is often considered alongside age-group guidelines. The standard clinical rule of thumb is 0.5 mg/kg/day for amphetamines (like Adderall) and 1.0 mg/kg/day for methylphenidate (like Ritalin). This tool provides a weight-based reference estimate alongside the age-group standard doses, so families and providers can compare both approaches. It is critically important to understand that Adderall is a Schedule II controlled substance, meaning it has a high potential for dependence and abuse. The FDA dosing guidelines represent conservative, evidence-based recommendations designed to maximize benefit while minimizing side effects and risk. Actual prescribing decisions must always be made by a licensed healthcare professional who knows the patient's full medical history, current medications, and individual circumstances. This calculator is intended as a reference tool for patients, caregivers, students, and healthcare professionals. It does not store any personal information, does not require an account, and runs entirely in your browser. All results come with a prominent disclaimer reminding users that professional medical guidance is always required.
Understanding Adderall Dosing
What Is Adderall and How Does It Work?
Adderall is a combination of amphetamine salts (75% dextroamphetamine, 25% levoamphetamine) that stimulates the central nervous system by increasing the release of dopamine and norepinephrine in the brain. These neurotransmitters are critical for attention regulation, impulse control, and executive function — all of which are impaired in individuals with ADHD. By boosting these signals, Adderall helps reduce hyperactivity, inattention, and impulsivity. The IR formulation is often used when precise timing or split dosing is needed, while the XR capsule is preferred for once-daily convenience. For narcolepsy, Adderall helps promote wakefulness by stimulating the same arousal pathways in the brainstem.
How Are Adderall Doses Determined?
FDA dosing recommendations for Adderall are based on age group, condition (ADHD vs. narcolepsy), and formulation (IR vs. XR). There is no universal weight-based formula in the FDA label, though clinicians often use 0.5 mg/kg/day as a rough guide. Titration — the process of gradually increasing doses — is mandatory: FDA guidelines specify starting doses and weekly increase increments to find the lowest effective dose. For conversion between ADHD medications, clinicians apply a class ratio (1 mg amphetamine ≈ 2 mg methylphenidate) combined with lookup tables that account for prodrug conversion efficiency (Vyvanse) and extended-release formulation differences (Concerta). This calculator uses those published ratios and tables.
Why Proper Dosing Matters
Underdosing Adderall leads to inadequate symptom control, which can impact academic performance, occupational function, and quality of life. Overdosing can cause cardiovascular side effects (elevated heart rate and blood pressure), insomnia, anxiety, decreased appetite, and in severe cases, psychosis or serotonin syndrome. Because Adderall is a Schedule II controlled substance, it also carries risks of misuse, diversion, and dependence when doses are not managed carefully. Following a structured titration protocol — starting low, going slow — is the safest way to find an effective dose while monitoring for adverse effects. Regular follow-up with a prescribing provider is essential.
Important Limitations of This Calculator
This tool provides general reference information based on FDA prescribing labels and published clinical guidelines. It cannot account for individual patient factors such as kidney or liver function, co-existing conditions (anxiety, bipolar disorder, cardiovascular disease), concurrent medications with potential interactions, genetic variation in drug metabolism (CYP2D6 polymorphisms), or prior medication history. The medication conversion estimates are approximations — actual equivalent doses vary from patient to patient. Children's doses in particular must be adjusted based on clinical response under close supervision. This calculator should never be used to self-prescribe, adjust doses without provider guidance, or replace a consultation with a licensed healthcare professional.
How to Use This Calculator
Choose Your Calculator Mode
Select 'Dosage Guide' to look up FDA-recommended doses for Adderall IR or XR by age group and condition. Select 'Medication Converter' to convert a current Adderall dose to an equivalent dose in another ADHD medication such as Vyvanse, Ritalin, or Concerta.
Enter Your Inputs
In Dosage Guide mode, choose your age group (3–5, 6–12, 13–17, or 18+), your condition (ADHD or narcolepsy), and your formulation (IR or XR). Optionally, enter your weight to see a weight-based dose reference and enter your tablet strength to calculate how many tablets per dose. In Converter mode, select your current medication, enter your dose in mg, and choose the target medication.
Review Your Results
The results show your starting dose, therapeutic dose range, FDA maximum, and weekly titration schedule. A visual progress bar shows where a starting dose sits relative to the maximum. The medication properties panel shows onset time, duration of action, and available tablet strengths.
Save or Share Your Results
Use the Copy or Share buttons to save your results, or click Print to generate a printer-friendly summary. The Export CSV button downloads all dosing data for offline reference. Always share results with your healthcare provider, not use them to make independent medication decisions.
Frequently Asked Questions
What is the typical starting dose of Adderall for adults?
For adults with ADHD, the FDA-approved starting dose of Adderall IR is 10–20 mg/day, typically divided into 2–3 doses taken 4–6 hours apart. For Adderall XR, the standard starting dose for adults is 20 mg once daily. Both formulations are then titrated upward by 5–10 mg per week as needed, up to a maximum of 40 mg/day for IR and 60 mg/day for XR. For narcolepsy, adults typically start at 10 mg/day and increase by 10 mg weekly. Individual dosing should always be determined by a licensed prescriber based on response and tolerability.
What is the maximum dose of Adderall?
The FDA-approved maximum daily dose of Adderall IR for ADHD is 40 mg/day across all age groups. For narcolepsy, the maximum is 60 mg/day. For Adderall XR, the maximum is 30 mg/day for children and adolescents (6–17) and 60 mg/day for adults. In clinical practice, some providers prescribe beyond these limits in carefully monitored cases — clinically used doses up to 80 mg/day are reported — but this is considered off-label and requires close monitoring. Never exceed your prescribed dose without medical supervision.
How does Adderall compare to Vyvanse?
Vyvanse (lisdexamfetamine) is a prodrug that is converted in the body to dextroamphetamine, making it pharmacologically similar to Adderall but with a slower onset and longer duration (8–12 hours vs. 8–10 hours for Adderall XR). The approximate conversion ratio is 1 mg Adderall ≈ 2.5 mg Vyvanse — so Adderall 20 mg ≈ Vyvanse 50 mg. Vyvanse is considered to have lower abuse potential because the prodrug form must be metabolized before it becomes active. The maximum FDA-approved dose of Vyvanse is 70 mg/day. Individual response may differ significantly from these averages.
What is the difference between Adderall IR and XR?
Adderall IR (Immediate Release) begins working within 30 minutes and lasts 4–6 hours. It is typically taken 2–3 times per day. Adderall XR (Extended Release) uses a bead system (50% immediate-release, 50% delayed-release) to provide an initial peak followed by a second release approximately 4 hours later, for a total duration of 8–10 hours. XR allows once-daily dosing, which improves adherence. Adderall IR gives more flexibility for dose timing (for example, avoiding a dose if symptoms are less severe in the afternoon). XR is not approved for children under 6 or for narcolepsy.
Is Adderall dosing based on body weight?
The FDA prescribing information for Adderall does not use weight-based dosing formulas. Instead, it specifies starting doses by age group and condition. However, many clinicians use a rule of thumb of 0.5 mg/kg/day for amphetamines as a rough reference — for example, a 40 kg child might aim for approximately 20 mg/day. This is not an official protocol and should not replace the age-group titration approach. Medications like atomoxetine (Strattera) do use explicit weight-based formulas in their FDA labeling (0.5–1.2 mg/kg/day for children under 70 kg).
How accurate are the medication conversion estimates?
The conversion estimates in this tool are based on published clinical equivalency ratios, most notably the cross-class ratio of 1 mg amphetamine ≈ 2 mg methylphenidate, and the NeuroLaunch equivalency table widely referenced in clinical practice. These are population-level averages, not precise individual predictions. Factors that can shift individual response include body weight, liver enzyme activity (CYP2D6 genetic variation), gastrointestinal pH, co-existing conditions, and prior medication history. Any medication switch should be supervised by a prescriber who can monitor your response and adjust the dose accordingly. These conversions should be treated as a starting point, not a final prescription.