Density of water at 25°C: measured 0.985 g/ml, theoretical 0.997 g/ml
% Error = (0.985 - 0.997) / 0.997 × 100 = -1.20%. Absolute: 1.20%. Excellent - chemistry lab acceptable range is typically under 2%.
Percent Error Calculator - Calculadora online grátis
Percent error measures how far an experimental value strays from a known theoretical or accepted value. Used in physics labs, chemistry titrations and engineering tests to express measurement accuracy.
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Percent error (signed)
-1.0204%
Undershoot
Absolute percent error
1.0204%
Difference
-0.1
Formula: % Error = (Experimental − Theoretical) / |Theoretical| × 100
Parte do conteúdo ainda aparece em inglês.
Entenda: Percent Error Calculator
Percent error is the standard metric for reporting accuracy of experimental measurements in science labs, engineering testing, and quality control. It compares an experimental (observed) value to a theoretical (accepted true) value and expresses the deviation as a percentage. Indian Class 11-12 physics, chemistry, and biology labs require percent error calculations in lab reports; engineering students compute it in physics labs through their B.Tech programmes; quality control engineers track percent error against specification tolerances.
Why percentage rather than absolute? Because a 5g error on a 50g sample is large (10%) while a 5g error on a 5kg sample is negligible (0.1%). Percent error scales with the value being measured, making it the universal accuracy metric across magnitudes. Most lab reports use absolute percent error (positive number, regardless of overshoot or undershoot). Some advanced contexts retain the sign to indicate bias direction - useful in calibration where you want to know if instruments systematically over-read or under-read.
Como usar Percent Error Calculator em 3 passos
Enter the experimental (observed) value.
Enter the theoretical (true) value.
See percent error and absolute percent error.
Como funciona Percent Error Calculator
Percent error keeps the sign of the difference - positive when you overshot, negative when you undershot. Most reports use absolute percent error since the magnitude is what matters for accuracy.
Formula
% Error = (Experimental − Theoretical) / |Theoretical| × 100%
- ExperimentalObserved / measured value
- TheoreticalAccepted / true value
Como Percent Error Calculator chega ao resultado
Formula: % Error = ((Experimental − Theoretical) / |Theoretical|) × 100. Signed version preserves direction (positive = overshoot, negative = undershoot). Absolute version: take absolute value of the entire expression, drops sign, reports magnitude only. Used for accuracy reports where sign isn't meaningful.
Acceptable percent error varies by context: School physics labs commonly tolerate 5-10% error before deducting marks. Chemistry titrations target under 2% for good technique. Industrial calibration of analytical instruments demands under 0.5%. NIST traceable measurements often require under 0.1%. Always know the acceptable threshold for your context before reporting.
Percent error vs percent difference: percent error compares to a known true value (the standard). Percent difference compares two experimental measurements where neither is the 'reference'. Use percent error in lab reports against textbook values; use percent difference when comparing two replicate measurements or two methods. Confusing the two is a common student mistake in lab writeups.
Exemplos resolvidos
Pendulum period: measured T = 2.05s, theoretical T = 2.00s
% Error = (2.05 - 2.00) / 2.00 × 100 = +2.5%. Acceptable for school physics lab. Source of error: human reaction time at start/stop.
Voltage measurement: measured 11.85V, expected 12.00V
% Error = (11.85 - 12.00) / 12.00 × 100 = -1.25%. Below 2% is typical for digital multimeter accuracy.
Quando usar Percent Error Calculator
- Class 11-12 physics, chemistry, biology lab reports.
- B.Tech engineering lab work - measurement and instrumentation.
- Quality control - comparing produced parts to spec tolerances.
- Calibration - checking instrument accuracy against known standards.
- Research - quantifying agreement between experiment and theory.
- Manufacturing - process control charts using percent error metrics.
- Pharmaceutical analysis - checking dosage accuracy.
- Chemistry titrations - verifying volumetric accuracy.
Erros e armadilhas comuns
- Mixing up experimental and theoretical values. Theoretical is the denominator.
- Reporting signed percent error when context expects absolute.
- Computing percent error when theoretical = 0 (undefined). Use absolute error instead.
- Confusing percent error with percent difference.
- Not reporting units of the original measurement alongside percent error.
Aproveite mais esta ferramenta
- Always identify which value is the 'known' or 'accepted' reference - that goes in the denominator.
- Report both signed and absolute percent error when bias direction matters (calibration).
- Pair percent error with absolute error when one of them is more interpretable in context.
- Sources of error in lab work: human reaction, instrument resolution, temperature drift, calibration drift.
- Pair with the percentage, statistics and standard deviation calculators on this site for related work.
Perguntas sobre Percent Error Calculator
Why use absolute percent error?
When magnitude is what counts (accuracy reports, lab grades), the sign isn't useful. Absolute error rolls up overshoot and undershoot into one number.
What is acceptable percent error?
Depends on context. School physics labs accept 5-10%. Chemistry titrations target <2%. Industrial calibration aims for <0.5%.
Can percent error be negative?
Yes - when experimental < theoretical. Some textbooks show signed error, others always show absolute. Check your course standard.
What if theoretical is zero?
Percent error is undefined when the true value is zero. Use absolute error in those cases.
How is percent error different from percent difference?
Percent error compares to a known true value. Percent difference compares two experimental values when neither is the reference.
Does percent error indicate precision or accuracy?
Accuracy - how close to the true value. Precision (repeatability) is captured by standard deviation of repeated measurements.
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