Research-use only. This guide covers general laboratory documentation and calculation checks. It is not medical advice and contains no dosing or administration instructions.
Why calculation records matter
A result is useful only when another competent reviewer can understand how it was produced. Good records show the source values, units, formula, conversions, assumptions, equipment and final reporting decision. They also make it easier to find errors before those errors are repeated.
1. Identify the calculation
Give every calculation a clear title, date and unique reference. State its purpose in neutral terms. Avoid vague labels such as “sample calculation” when several samples or methods are involved.
2. Preserve the source data
Copy source values exactly as recorded and retain a link or reference to the original record. Never overwrite the original measurement with a converted or rounded value. A reviewer should distinguish measured data from calculated data.
3. Record every unit
Write units beside every number, including intermediate results. If milligrams are converted to micrograms, show the factor: 1 mg = 1,000 µg. If millilitres are converted to microlitres, show 1 mL = 1,000 µL. This dimensional trail is a strong defence against thousand-fold errors.
4. State the formula
Write what the formula means before entering values. For example, concentration equals amount divided by final volume. Then show the symbolic expression and substituted values. The research calculator supports arithmetic, but the record must explain why those inputs were selected.
5. Define each volume
Distinguish starting, added and final volume. Note whether the method assumes volumes are additive. The guide to final and added volume explains why an ambiguous denominator can change a result.
6. Identify equipment
Record the instrument used, its identifier, capacity and calibration or verification status where relevant. A number entered from an unverified device should not be treated as having unlimited precision.
7. Keep the unrounded result
Retain guard digits during intermediate steps. Record the unrounded result and the rounded reported value, together with the rounding rule. See Significant Figures and Measurement Uncertainty.
8. Record assumptions
Assumptions should never be hidden. Examples include assumed additivity of volumes, use of a nominal rather than measured value, or reliance on a stated certificate value. If an assumption cannot be justified by the procedure, stop and seek clarification.
9. Perform an independent check
Use a second method, estimate the order of magnitude, or ask another trained person to reproduce the calculation. Re-entering the same numbers into the same formula is not fully independent.
10. Protect the audit trail
Corrections should remain visible. Record what changed, why it changed, who made the change and when. Electronic systems should retain version history or equivalent controls.
Reusable record template
- Record ID and date
- Purpose
- Source data and references
- Formula and definitions
- Unit conversions
- Substituted values
- Unrounded result
- Reported result and rounding rule
- Equipment identifiers
- Assumptions and limitations
- Independent check
- Reviewer and approval date
Final review questions
- Can a reviewer reproduce the calculation without asking what a number means?
- Are all units consistent?
- Is the final volume clearly identified?
- Are conversions and rounding visible?
- Are limitations stated honestly?
For the core arithmetic, visit How It Works. The educational collection is on the Research Guides page.