Calcium Dietary-Gap Calculator

Life-stage drives the daily target: 1000 mg/day for adults 19–70 and pregnancy; 1200 mg/day for postmenopausal women and adults 70+. The tolerable upper limit is 2500 mg/day under 50 (including pregnancy) and 2000 mg/day above 50.

Dietary intake is estimated as: (dairy servings × 300 mg) + (leafy-greens cups × 200 mg) + (fortified servings × 300 mg) + 200 mg residual baseline (mixed-diet contribution from non-dairy non-leafy sources). Supplemental dose is the gap to target, rounded to the nearest 50 mg, then split at ≤500 mg per dose to stay under the active-transport saturation threshold (calcium absorption plateaus near that ceiling per discrete intake).

Form selection: carbonate (~30% absorption) requires gastric acid and is taken with meals; citrate (~35% absorption) is acid-independent and works any time. The calculator forces citrate when on a PPI (acid suppression) or at age 70+ (lower baseline gastric acid). Otherwise the form preference is respected.

CVD flag priority: (1) UL exceeded — total intake (diet + supplement) above the life-stage UL fires a hard stop. (2) Diabetic supplementer — Qiu 2024 (PMID 37506393) found CVD mortality HR 1.67 in this group; the calculator hard-stops supplemental dose and redirects to dietary sources. (3) Non-diabetic supplementer above 1000 mg/day — Chen 2025 (PMID 40315789) AF/AFL HR 1.20 + Reid 2025 (PMID 39937345) post-bolus coagulability rise; the calculator fires an amber warning. The 2025 Cochrane preeclampsia review (PMID 41330480) downgraded calcium's hypertensive-disorder evidence to little-to-no-difference (RR 0.83, CI 0.67–1.04) — pregnancy supplementation is not recommended in adequate-calcium populations.

Bone stack: calcium alone has weaker fracture-prevention evidence than calcium + vitamin D3 + vitamin K2 + magnesium. Yao 2019 (PMID 31860103) is the cleanest data — 6% any-fracture, 16% hip-fracture reduction in pooled D3 + Ca trials. The calculator surfaces the stack pairing on every result.