C₁V₁ = C₂V₂ for cell suspensions
Accurate cell seeding is critical for reproducible experiments. Using C₁V₁ = C₂V₂: V₁ = (C₂ × V₂) / C₁. For example, to seed a T-75 flask at 2 × 10⁵ cells/mL in 15 mL from a suspension of 10⁶ cells/mL: V₁ = (2×10⁵ × 15) / 10⁶ = 3 mL of suspension + 12 mL fresh media. Typical seeding densities: HeLa cells 5×10⁴/cm², CHO cells 3×10⁵/mL for suspension, primary cells vary widely. Under-seeding leads to slow growth; over-seeding causes contact inhibition and early confluency. Always count cells accurately (hemocytometer or automated counter) and verify viability with trypan blue before diluting.