Insulin Dose Calculator
Medically reviewed by Dr. Chhaya Makhija, MD, DipABLM — October 2026
The complete dosing walkthrough: estimate your total daily dose (TDD) from weight, split it into basal and bolus, and derive your insulin-to-carb ratio (500 Rule) and correction factor (1800 Rule) — with every formula shown.
💉 Full Insulin Dose Calculator
Estimated Results
Estimated Total Daily Dose (TDD)
(long-acting)
(across meals)
X g carbs (500 Rule)
BG by X mg/dL (1800 Rule)
How to Use the Insulin Dose Calculator
Enter Weight
Type your weight in kg or lbs — the value converts automatically when you toggle units.
Pick a Dose Factor
0.5 u/kg is the ADA's typical start for a stable adult with type 1 diabetes. Type 2 basal-only starts use 0.1–0.2 u/kg.
Choose the Split
50/50 is the common teaching default; some clinicians prefer 40% basal / 60% bolus.
Read All Four Numbers
TDD, basal dose, ICR and ISF are calculated together — the same chain your care team uses.
Check the Formulas
Every step of the math is printed below the result so you can verify or share it.
Confirm With Your Team
These are population starting estimates. Your provider confirms, adjusts, and titrates them.
The Complete Insulin Dosing Chain, Explained
Clinicians estimate insulin doses in a chain of four linked calculations. Each step feeds the next, which is why this page calculates them together rather than in isolation.
Step 1 — Total Daily Dose (TDD)
Worked example: 75 kg × 0.5 = 37.5 units/day. Working in pounds? A long-standing clinical shortcut divides body weight in pounds by 4: a 165 lb adult lands near 41 units/day, which matches roughly 0.55 u/kg. Insulin-naïve Type 2: 75 × 0.2 = 15 u/day (or a fixed 10 u basal start). Explore this step in depth with the Dose by Weight Calculator or TDD Calculator.
Step 2 — Basal / Bolus Split
Worked example: 37.5 u TDD → basal ≈ 19 u once daily (long-acting), bolus pool ≈ 18.5 u divided across meals. See the Basal-Bolus Calculator for regimen details.
Step 3 — Insulin-to-Carb Ratio (500 Rule)
Worked example: 500 ÷ 37.5 ≈ 1 unit per 13 g carbs. A 65 g-carb meal → 65 ÷ 13 = 5 units. Using Regular insulin? Use the 450 Rule instead. Full detail: ICR Calculator.
Step 4 — Insulin Sensitivity Factor (1800 Rule)
Worked example: 1800 ÷ 37.5 = 48 mg/dL (2.7 mmol/L) per unit. At 220 mg/dL (12.2 mmol/L) with a 120 target: (220 − 120) ÷ 48 ≈ 2 units correction — minus any insulin on board. Full detail: ISF Calculator and Correction Dose Calculator.
Clinicians use more than one divisor here. The 1800 Rule suits rapid-acting analogues. Davidson’s work on insulin dosing uses 1700, which produces a slightly stronger correction, and some teams use 2000 for people who are highly insulin-sensitive. A larger divisor yields a larger ISF, so each unit is credited with lowering glucose further and the correction dose shrinks. Ask your team which divisor your regimen assumes before acting on a number.
Titration: where the real dose comes from
Weight-based math produces a starting estimate only. The actual working dose emerges over 2–6 weeks of titration: fasting glucose guides basal adjustments (a common outpatient pattern is +2 units every 3 days until fasting glucose is in target, per ADA guidance), while post-meal readings refine the ICR, and correction outcomes refine the ISF. Expect your care team to adjust each number independently — most people do not end up on exactly the formula values.
Renal impairment, steroid therapy, pregnancy, and pediatric care all change these formulas materially. Use the dedicated tools: pediatric, pregnancy, steroid-induced hyperglycemia.
Starting Insulin Dose by Diabetes Type
The starting factor depends on the diagnosis, and the three cases differ sharply. Type 1 needs full insulin replacement from the first day. Type 2 usually starts with basal insulin alone, on top of existing oral medication. Pregnancy raises insulin requirements through every trimester. Find the row that matches your situation, then confirm the figure with your care team.
| Diabetes type | Typical starting dose | What the dose covers | Dedicated tool |
|---|---|---|---|
| Type 1 | 0.5 u/kg/day when stable; 0.2–0.6 u/kg/day at new onset | Full basal plus bolus replacement | Type 1 insulin calculator |
| Type 2 | 0.1–0.2 u/kg/day, or a flat 10 units of basal | Basal only at first, alongside oral agents | Type 2 insulin calculator |
| Pregnancy | Rises by trimester: about 0.6–0.7, then 0.7–0.9, then 0.9–1.1 u/kg/day | Tighter glucose targets and frequent adjustment | Pregnancy insulin calculator |
Type 1 and Type 2 figures follow the ADA Standards of Care in Diabetes — 2026 ranges cited below. Pregnancy factors climb through gestation and belong with a specialist team rather than a starting formula.
Quick Reference: Starting TDD by Body Weight
Estimates at 0.4, 0.5 and 0.6 u/kg/day, the lower part of the ADA's typical 0.4–1 u/kg/day range. Values rounded to the nearest unit.
| Weight (kg) | Weight (lbs) | Low — 0.4 u/kg | Mid — 0.5 u/kg | High — 0.6 u/kg |
|---|---|---|---|---|
| 50 | 110 | 20 u | 25 u | 30 u |
| 60 | 132 | 24 u | 30 u | 36 u |
| 70 | 154 | 28 u | 35 u | 42 u |
| 80 | 176 | 32 u | 40 u | 48 u |
| 90 | 198 | 36 u | 45 u | 54 u |
| 100 | 220 | 40 u | 50 u | 60 u |
| 110 | 243 | 44 u | 55 u | 66 u |
| 120 | 265 | 48 u | 60 u | 72 u |
Insulin Dose Calculator: Limitations & Safety Notes
- The 500/1800 Rules assume rapid-acting analog insulin. Regular insulin uses the 450/1500 Rules.
- Formulas do not account for insulin on board, activity, illness, alcohol, or gastroparesis.
- Do not apply adult formulas to children — pediatric dosing requires specialist supervision.
- Renal or hepatic impairment reduces insulin clearance; standard formulas may overestimate need.
This page is the general-purpose entry point; the main insulin calculator hub links out to every specialised version.
Sources & References
- American Diabetes Association. Standards of Care in Diabetes — 2026. Section 9: Pharmacologic Approaches. Link
- Walsh J, Roberts R. Using Insulin: Everything You Need for Success with Insulin. (Origin of the 500/1800 Rules.)
- Davidson PC, et al. Analysis of guidelines for basal-bolus insulin dosing. Endocr Pract. 2008.
- NIDDK. Insulin Medicines & Treatments. Link
Written by Ryan Mitchell · Last updated: October 2026
Frequently Asked Questions: Insulin Dose Calculator
How do I calculate my insulin dose?
Start with total daily dose: for Type 1, weight (kg) × 0.4–1.0 u/kg/day, with 0.5 the usual midpoint; Type 2 usually starts lower at 0.1–0.2 u/kg or a flat 10 units. Split it ~50% basal / 50% bolus. Then derive your carb ratio (500 ÷ TDD) and correction factor (1800 ÷ TDD). Each meal dose = carbs ÷ ICR, plus (current − target BG) ÷ ISF when above target. Confirm every value with your care team before use.
What is the 500 Rule and the 1800 Rule?
The 500 Rule (500 ÷ TDD) estimates how many grams of carbohydrate one unit of rapid-acting insulin covers. The 1800 Rule (1800 ÷ TDD) estimates how far one unit drops blood glucose in mg/dL. Regular insulin uses the 450 and 1500 Rules instead — see our 450 Rule calculator.
How much insulin do I need per day?
Type 1 totals usually land between 0.4 and 1.0 units/kg/day — about 35 units for a 70 kg adult at the 0.5 midpoint. Insulin-naïve Type 2 patients usually begin far lower (0.1–0.2 u/kg or 10 units basal). People with significant insulin resistance may need considerably more over time. The starting number is only a launch point for supervised titration.
What is the difference between basal and bolus insulin?
Basal insulin is the long-acting background dose (40–50% of TDD) covering fasting periods and overnight. Bolus insulin is rapid-acting insulin at meals covering carbohydrates and corrections (the remaining 50–60%, split across meals). Our basal-bolus calculator models the full regimen.
Is this calculator safe to use for dosing decisions?
It is an educational tool showing the standard published formulas so you can understand where your prescribed numbers come from. It is not a dosing device and not medical advice. Never start or change insulin without your doctor or diabetes care team.