What to look for in free health tools: cited guidelines, transparent formulas, privacy-friendly defaults, and validation steps. Each page links to our matching calculator.
The best free BMI calculators in 2026 show CDC adult categories or pediatric percentiles, explain that BMI screens rather than diagnoses body fat, and work without creating an account. Prefer tools that cite NHLBI or CDC pages and offer metric and US units.
Strong free TDEE calculators in 2026 use Mifflin-St Jeor or Harris-Benedict with labeled activity multipliers, show BMR and TDEE separately, and remind you that labels on food and daily steps still need a one to two week validation period.
Top free blood sugar converters in 2026 multiply mmol/L by 18.0182 to get mg/dL (or divide the other direction), display both units side by side, and link ADA diagnostic thresholds without replacing lab-confirmed results.
The best free body fat calculators in 2026 name the underlying method (for example Navy circumference equations), give sex-specific ranges, and warn that home methods carry roughly 3 to 5 percentage point error even with good technique.
Quality free macro calculators in 2026 start from your calorie target, set protein in grams per kilogram (often 1.2 to 2.0 g/kg depending on activity), then fill remaining calories with carbs and fat inside AMDR bands (10 to 35% protein, 45 to 65% carbs, 20 to 35% fat).
The best free blood pressure calculators in 2026 map systolic and diastolic pairs to ACC/AHA categories (normal below 120/80, elevated, stage 1, stage 2), note that diagnosis requires repeated measurements, and link home monitoring protocols from heart.org.
Reliable free A1c calculators in 2026 use the ADAG linear equation for estimated average glucose, show ADA cutoffs (5.7% prediabetes, 6.5% diabetes when confirmed), and state that only certified lab A1c should drive medication changes.
The best free due date calculators in 2026 apply Naegele rule for regular cycles, let you enter ultrasound dates when LMP is uncertain, and explain that only about 4% of babies arrive on the exact estimated date.
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