Free, sourced calculators for everyday decisions.
No signup, no paywall, no invented numbers — every figure links to its source.
Pet & Vet
Dog Chocolate Toxicity Calculator Estimate theobromine risk from your dog’s weight, chocolate type, and amount eaten. Try it Dog Age Calculator Your dog’s age in human years, adjusted for size — not the old ×7 myth. Try it Dog Food Portion Calculator How much to feed your dog, based on their weight, life stage, and food’s calorie content. Try it Pet Insurance Cost Calculator Estimate average monthly pet insurance premiums by pet type and coverage tier. Try it
Sleep & Rest
Sleep Cycle Calculator Find bedtimes or wake-times that land on a 90-minute sleep-cycle boundary. Try it Nap Calculator The best nap length to avoid grogginess, and the latest time to nap without wrecking tonight’s sleep. Try it Caffeine Cutoff Calculator What time to stop caffeine, based on your bedtime and caffeine’s ~5-hour half-life. Try it Baby Sleep Schedule Calculator Typical total daily sleep by age (0–60 months), sourced to pediatric sleep guidelines. Try it
About Hearth
Hearth is an independent project built around one rule: every number on the page has to trace back to a real, citable source — a veterinary manual, a published guideline, a peer-reviewed figure — never a plausible-sounding guess. Most "quick calculator" sites optimize for looking authoritative; Hearth optimizes for actually being right, and shows its work so you can check.
No accounts, no tracking beyond aggregate, privacy-respecting analytics, and nothing to buy — see the privacy policy for the specifics.