How to Use the Insulin Calculator
Follow these steps to generate an educational dose estimate in under a minute.
Enter Your Weight
Type your body weight and choose kilograms (kg) or pounds (lbs). The calculator converts automatically.
Select Diabetes Type
Choose Type 1 or Type 2. The dosing factor changes slightly — Type 2 insulin-naïve patients often start at a lower dose.
Choose Insulin Type
Rapid-acting analogs use the 1800 Rule; Regular (human) insulin uses the 1500 Rule for sensitivity factor.
Enter Blood Glucose (Optional)
Add your current blood glucose and target to get a correction dose estimate. Choose mg/dL or mmol/L.
Click Calculate
Results appear instantly. The full calculation — including the formula — is shown below the result so you can verify the math.
Discuss With Your Provider
Copy or print the estimate and bring it to your next appointment. Never adjust your dose without consulting your diabetes care team.
How This Calculator Works — Formulas Explained
Every estimate is based on standard formulas published in peer-reviewed diabetes literature and endorsed by major clinical organizations.
Total Daily Dose (TDD)
The American Diabetes Association (ADA) and AACE recommend a weight-based starting dose of 0.4–0.6 units/kg/day for most adults. This calculator uses 0.5 u/kg as the midpoint estimate for Type 1, and 0.2 u/kg as a conservative starting point for insulin-naïve Type 2 patients. Worked example: a 70 kg adult with Type 1 → TDD = 70 × 0.5 = 35 units/day.
Insulin-to-Carb Ratio — The 500 Rule
The 500 Rule estimates how many grams of carbohydrate one unit of rapid-acting insulin covers. If TDD = 35, then ICR = 500 ÷ 35 ≈ 14.3 — meaning one unit covers roughly 14g of carbohydrates. Source: Walsh et al., "Using Insulin" (widely cited in ADA/AACE patient guidelines).
Insulin Sensitivity Factor (ISF) — The 1800 / 1500 Rule
ISF estimates how much blood glucose (in mg/dL) drops per unit of insulin. With TDD = 35 and rapid-acting insulin, ISF = 1800 ÷ 35 ≈ 51 mg/dL per unit. Source: Davidson PC et al., Diabetes Care 2003; Wolpert HA et al.
Correction Dose
If current BG = 220 mg/dL, target = 100 mg/dL, and ISF = 51, correction dose = (220 − 100) ÷ 51 ≈ 2.4 units. This calculator rounds to the nearest 0.5 unit as is common clinical practice. Always confirm with your care team before dosing.
These formulas provide initial estimates only. Individual insulin requirements vary due to activity, diet, concurrent medications, kidney function, stress, and many other factors. Your actual doses should always be set by your diabetes care team through individual titration.
Why This Calculator Is Reliable
Standard Clinical Formulas
Every formula is sourced from ADA, AACE, or peer-reviewed literature — the same ones used in clinical practice. Sources are cited on every page.
Transparent Calculations
The full formula and your specific numbers are shown with every result, so you can verify the math yourself or share it with your provider.
mg/dL and mmol/L Support
Toggle between US (mg/dL) and international (mmol/L) units. All conversions happen automatically in the browser.
Input Validation & Warnings
Implausible values trigger soft warnings. The calculator never silently produces results from obviously wrong inputs.
Works on Any Device
Fully responsive — use it on a phone in the waiting room, a tablet, or a desktop. No app download, no login, completely free.
Privacy First
All calculations run entirely in your browser. No health data is ever sent to a server or stored anywhere.
Safety Notes & Limitations
This tool is for educational and informational purposes only. It does not constitute medical advice, diagnosis, or treatment. The formulas used are well-established starting-point estimates — they cannot account for your individual physiology, comorbidities, activity level, food composition, other medications, or the judgement of a trained clinician.
- Estimates are most applicable to adults; pediatric dosing requires specialist input.
- Pregnancy and gestational diabetes require closer medical supervision — do not rely on general formulas.
- Renal or hepatic impairment significantly alters insulin requirements and is not modeled here.
- If you experience symptoms of severe hypoglycemia (shakiness, confusion, loss of consciousness) or DKA (nausea, vomiting, fruity breath, high ketones), seek emergency medical care immediately.
Sources & References
- American Diabetes Association. Standards of Medical Care in Diabetes. Diabetes Care, 2024. ADA Standards of Care
- AACE/ACE. Comprehensive Type 2 Diabetes Management Algorithm. Endocr Pract. 2020. AACE Guidelines
- Davidson PC et al. "The 1500 and 1800 Rules." Diabetes Care 2003; published online. Reference widely used in ADA patient resources.
- Walsh J, Roberts R, Bailey T. "Guidelines for Optimal Bolus Calculator Settings in Adults." J Diabetes Sci Technol. 2011;5(1):129-135.
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Insulin, Medicines, & Other Diabetes Treatments. NIDDK
Last reviewed: June 2025 · Formulas reviewed against cited sources above
Frequently Asked Questions
How do I calculate my insulin dose?
A common starting estimate uses the Total Daily Dose (TDD) formula: TDD = body weight in kg × 0.4–0.6 units. This calculator uses 0.5 u/kg for Type 1 and a conservative 0.2 u/kg for insulin-naïve Type 2. From TDD, you can estimate your insulin-to-carb ratio (500 ÷ TDD) and insulin sensitivity factor (1800 ÷ TDD for rapid-acting). Always confirm any calculated dose with your diabetes care team before making changes.
What is the 500 rule for insulin?
The 500 Rule estimates your insulin-to-carb ratio (ICR): divide 500 by your total daily insulin dose. The result is approximately how many grams of carbohydrates one unit of rapid-acting insulin will cover. For example, if your TDD is 50 units, your estimated ICR is 500 ÷ 50 = 1 unit per 10g of carbs. This is a starting estimate — your actual ratio should be confirmed with your provider.
What is insulin sensitivity factor (ISF)?
Insulin sensitivity factor (ISF), also called correction factor, estimates how much one unit of rapid-acting insulin lowers your blood glucose. It is calculated using the 1800 Rule: ISF = 1800 ÷ TDD. If your TDD is 50 units, ISF ≈ 36 mg/dL — meaning one unit should lower blood glucose roughly 36 mg/dL. This varies significantly between individuals; your care team will help you find your actual ISF through real-world testing.
Is this insulin calculator safe to use?
This calculator applies standard published formulas to generate educational estimates, but it does not account for your individual physiology, medication interactions, activity level, illness, or other factors your care team considers. It is designed for learning, discussion, and preparation for provider conversations — not for autonomous dosing decisions. Never use these estimates to change your insulin dose without consulting your doctor or certified diabetes care and education specialist (CDCES).
What is a normal total daily insulin dose?
According to ADA and AACE guidelines, a typical starting total daily dose for adults is 0.4–0.6 units per kilogram of body weight per day. A 70 kg adult might start at 28–42 units/day split between basal and bolus. People with Type 1 diabetes often use 0.4–0.5 u/kg, while insulin-naïve Type 2 patients may start conservatively at 0.2 u/kg or a fixed 10 units/day and titrate up. Actual TDD varies widely and is always determined by your care team.