Use this chemistry calculator to reproduce a named relationship with explicit quantities and units for study, laboratory planning, or an independent numerical check.

Initial amount

Starting amount N₀.

Half-life (s)

Half-life of the decaying substance; must be greater than zero.

Elapsed time (s)

Elapsed time.

Compute the remaining amount after radioactive decay as N = N₀·(1/2)^(t/t½). The tool evaluates the supplied inputs together and returns the named outputs below; it does not infer omitted operating conditions or change the units shown.^[1]

Remaining amount

Amount remaining.

Fraction remaining

Remaining fraction of the initial amount.

• Radioactive and nuclear calculations require the correct isotope, decay mode, mass convention, and time unit. Branching, daughter products, detector efficiency, shielding, and uncertainty in tabulated nuclear data may require a fuller model.
• Use finite inputs in the displayed units and preserve more precision than the final presentation requires. Independently verify safety-critical, financial, compliance, or production decisions.

Check units and significant figures, compare the result with limiting cases, and use measured or source-specific constants where available. Laboratory, safety, and regulatory decisions require validated methods and appropriate uncertainty analysis.

• Activity Decay Calculator

  Compute the radioactive activity after a time as A = A₀·e^(−λt) with λ = ln2/t½.

• Decay Half-Life Calculator

  Solve the half-life from an initial amount, a remaining amount, and the elapsed time as t½ = t·ln2 / ln(N₀/N).

• Buffer pH After Addition

  Compute the buffer pH after adding strong base as pKa plus log10 of conjugate base over remaining weak acid.