Vitamin D Calculator
Dose to reach a target blood level.
Enter your values
Enter the current 25(oh)d in ng/mL.
Enter the target level in ng/mL.
Enter the body weight in kg.
Results update instantly as you type — no submit needed. Your values are remembered on this device, and the shareable link reopens the calculator with exactly these numbers.
- Suggested daily dose
- 6,100 IU
- Level gap to close
- 22 ng/mL
- Target in nmol/L
- 100
- Current status
- Deficient
- Time to steady state
- 8–12 weeks
Quick answer
Each 1000 IU of daily vitamin D3 raises serum 25(OH)D by roughly 10 nmol/L (4 ng/mL) at steady state.
At a glance
| What it does | Dose to reach a target blood level. |
|---|---|
| Category | Health |
| Inputs needed | Current 25(OH)D, Target level, Body weight |
| Main output | Suggested daily dose |
| Cost | Free — no sign-up, no download |
How to use the Vitamin D Calculator
- 1Enter your current 25(OH)D blood level.
- 2Enter your target level (30–50 ng/mL is typical).
- 3Enter body weight for dose adjustment.
Inputs explained
- Current 25(OH)D(ng/mL)
- Enter the current 25(oh)d in ng/mL.
- Target level(ng/mL)
- Enter the target level in ng/mL.
- Body weight(kg)
- Enter the body weight in kg.
Worked example
Using the values the calculator loads with:
Inputs
- Current 25(OH)D18 ng/mL
- Target level40 ng/mL
- Body weight78 kg
Results
- Suggested daily dose6,100 IU
- Level gap to close22 ng/mL
- Target in nmol/L100
- Current statusDeficient
- Time to steady state8–12 weeks
Frequently asked questions
What is the safe upper limit?
4000 IU a day for most adults without medical supervision.
Should I retest?
Yes, after about three months of consistent supplementation.
What do I need to enter into the Vitamin D Calculator?
Just 3 values: current 25(oh)d, target level, body weight. Every field starts with a realistic example, so you can change one number at a time and watch the result update instantly.
How does the Vitamin D Calculator work out the answer?
Each 1000 IU of daily vitamin D3 raises serum 25(OH)D by roughly 10 nmol/L (4 ng/mL) at steady state. The working is shown step by step so you can verify the result by hand.
Is the Vitamin D Calculator free, and do I need an account?
It is completely free with no sign-up, no download and no usage limit. Everything is calculated in your browser, so the numbers you type never leave your device.
Results are estimates for general information. For medical, legal, structural or financial decisions, confirm with a qualified professional.