Vitamin C Daily Need Calculator
Find recommended Vitamin C intake from age, sex, and smoking status per NIH.
Returns RDA, tolerable upper limit, food source rankings, and supplement guidance.
Vitamin C (ascorbic acid) is an essential water-soluble vitamin that the human body cannot synthesize on its own — it must come entirely from diet or supplements. It plays critical roles in collagen synthesis, immune function, iron absorption, and antioxidant defense.
Recommended Dietary Allowances (RDA) by age and group:
- Infants 0–6 months — 40 mg/day (AI)
- Infants 7–12 months — 50 mg/day (AI)
- Children 1–3 years — 15 mg/day
- Children 4–8 years — 25 mg/day
- Children 9–13 years — 45 mg/day
- Teens 14–18 (male) — 75 mg/day
- Teens 14–18 (female) — 65 mg/day
- Adult males — 90 mg/day
- Adult females — 75 mg/day
- Pregnant women — 85 mg/day
- Breastfeeding women — 120 mg/day
- Smokers — add 35 mg/day to all above (smoking depletes vitamin C)
Tolerable Upper Intake Level (UL): 2,000 mg/day for adults Exceeding the UL may cause: nausea, diarrhea, abdominal cramps, kidney stones (oxalate pathway).
Bioavailability formula (absorption efficiency):
- At doses ≤200 mg: ~90% absorbed
- At 500 mg: ~73% absorbed
- At 1,000 mg: ~50% absorbed
- At 2,000 mg: ~20% absorbed — higher doses yield diminishing returns
Worked example: Adult male smoker: RDA = 90 + 35 = 125 mg/day. Takes a 500 mg supplement. Absorption ≈ 73%. Absorbed dose = 500 × 0.73 = 365 mg — well above the RDA with comfortable margin below the 2,000 mg UL.
Top dietary sources of vitamin C:
- Bell peppers (red): 190 mg per 100g
- Kiwi: 93 mg per 100g
- Broccoli: 89 mg per 100g
- Strawberries: 59 mg per 100g
- Orange juice: 50 mg per 100g
- One medium orange: ~70 mg
Vitamin C is heat-sensitive — cooking can destroy 15–55% of content. Raw or lightly steamed vegetables retain the most.