About Insulin Point
A free insulin calculator and a set of plain-language guides, built and written by one person. This page explains who that is, how the numbers are worked out, and where the tool stops being useful.
Why I built it
Working out an insulin dose involves several steps of arithmetic: a carb ratio, a correction factor, insulin still active from the last dose, and rounding to what a pen or pump can actually deliver. Each step is simple on its own. Done in your head before a meal, they are easy to get wrong, and a small slip can mean a low or a high.
The rules themselves are published and widely taught, but they are scattered across textbooks, clinic handouts and pump manuals. I built Insulin Point to put them in one place, show every step of the working, and run entirely in your browser. There is no account, and nothing you enter is sent anywhere.
What Insulin Point Calculates
Meal Bolus (500 Rule)
Calculates your Insulin-to-Carb Ratio (ICR) using the 500 Rule: ICR = 500 ÷ TDD. Then works out the units for a given carbohydrate amount.
Correction Bolus (1800 Rule)
Derives your Insulin Sensitivity Factor (ISF) via the 1800 Rule: ISF = 1800 ÷ TDD. Works out correction units from your current and target glucose.
Active IOB Decay Guard
Models insulin-on-board decay for rapid-acting insulin. Subtracts insulin still active from earlier doses to help avoid stacking.
TDD & Basal/Bolus Split
Profiles your Total Daily Dose and calculates the recommended 50/50 basal-to-bolus split. Estimates starting doses from body weight for newly initiated insulin therapy.
Rx Days Supply & BUD
Calculates pharmacy days supply from vial size, concentration, and daily dose. Applies manufacturer Beyond-Use Dating (BUD) limits for opened pens and vials.
Guides & FAQ
Plain-language guides on insulin types, dosing rules, lows and highs, and storage, plus answers to common questions.
How it is built
- ✓ Privacy-first: All calculations run entirely in your browser. No form data, glucose readings, or personal information is ever transmitted or stored on a server.
- ✓ Published rules only: Every formula is a standard, published rule of thumb (500 Rule, 1800 Rule, weight-based starting doses, IOB decay). The formulas page shows each one and the references behind it.
- ✓ Always free: Insulin Point is and will remain completely free with no subscriptions, premium tiers, or paywalls. The site is supported by ads.
- ✓ Dual unit support: All blood glucose values support seamless switching between mg/dL (US) and mmol/L (international) — without reloading or re-entering data.
Who built this
Bibek Sharma
Software Engineer · B.Tech, Computer Science
I'm a software engineer. I built the calculators and wrote the guides on this site. The dosing rules come from the published references listed on the formulas page, and the calculation code has automated tests.
I'm not a doctor, pharmacist, nurse or diabetes educator, and no clinician has reviewed these pages. Read them as an explanation of how the standard rules work, not as instructions for your own doses.
You can find me on LinkedIn. If you spot a mistake, the contact page reaches me directly, and corrections from clinicians are especially welcome.
Its limits
The rules this site uses are starting points. Clinicians use them to set an initial ratio or correction factor, then adjust from your actual glucose readings. Your own settings may be quite different, and the ones your care team gave you always take priority over anything calculated here.
The calculator can't account for illness, exercise, alcohol, other medications, pregnancy, or the way your body responds on a given day. If a result looks different from what you'd expect, trust your care team's plan and your meter, not the web page.