Substrate Concentration From Volume Guide
Purpose
Substrate concentration is a basic value in assay design. It tells how much reactive material exists in a final mixture. A small volume of strong stock can change an entire reaction. This calculator helps estimate that final value from common inputs. It supports stock solutions, weighed substrate, known moles, and dilution factors.
Why Volume Matters
Volume controls dilution. When stock substrate is added to buffer, the same moles spread through a larger solution. The concentration therefore falls. Accurate volume entry is important for kinetic assays, calibration curves, and preparation logs. Microliter errors can become large in small wells or cuvettes.
Stock Solution Method
The stock method uses concentration and transferred volume. The calculator first converts the stock concentration to molar units. It also converts the added and final volumes to liters. Then it multiplies stock concentration by added volume. That gives the amount of substrate. Finally, it divides by total final volume. The result can be shown as M, mM, µM, or nM.
Mass Method
The mass method is useful when a dry substrate is weighed. The calculator converts the mass to grams. It divides grams by molecular weight. That step gives moles. The moles are then divided by final volume in liters. This gives molar concentration. Use a correct molecular weight, including salt or hydrate form when needed.
Moles and Dilution Method
The moles method is direct. It only needs amount and final volume. The dilution factor method is faster for serial dilutions. It divides the original concentration by the dilution factor. Both methods are helpful for standards and repeated assay setups.
Good Practice
Always confirm units before calculation. Keep final volume as the total mixture volume, not only the solvent volume. Record assumptions in the notes field. Export results when a worksheet or lab record is needed. Review the formula line to confirm that the selected mode matches your experiment.