Percent Error Calculator Compute error in experiments, labs, and engineering — with 2025 benchmarks, uncertainty insights...

Percent Error Calculator

Compute error in experiments, labs, and engineering — with 2025 benchmarks, uncertainty insights, and reporting standards.

Percent Error

Percent Difference

Absolute Error

Experimental Value

Theoretical / Accepted Value

Units

Value A

Value B

Units

Experimental

Theoretical

Units

0.0%

Percent Error

0.00

Absolute Error

0.000

Relative Error

—

Uncertainty

Error Visualization

Error Formulas

Percent Error** (accuracy):

$$ \text{Error \%} = \left| \frac{E - T}{T} \right| \times 100\% $$

Percent Difference** (precision):

$$ \text{Diff \%} = \frac{|A - B|}{(A + B)/2} \times 100\% $$

Absolute Error**:

$$ \text{Error} = |E - T| $$

Example** (g = 9.65 m/s² vs. 9.81 m/s²): • Absolute error = |9.65 − 9.81| = **0.16 m/s²** • Percent error = |−0.16 / 9.81| × 100% = **1.63%** → **Good** (1–5% range)

✅ Pro Tip**: Always include **uncertainty** (e.g., ±0.05 m/s²) in lab reports — it defines error bounds.

Error Calculation Red Flags

⚠️ Avoid these common mistakes:

• Dividing by experimental value** — Must use *theoretical* in denominator for % error
• Ignoring significant figures** — Report error with *same decimal places* as uncertainty (e.g., 9.65 ± 0.05)
• Confusing accuracy & precision** — Low % error = accurate; low % diff = precise
• Omitting units** — Absolute error has units; % error is unitless

✅ Best Practices**:

• Use **relative error** for cross-experiment comparison: Error / Theoretical
• For multiple trials: report *mean ± std dev*, then compute % error on mean
• In engineering: compare error to **tolerance spec** (e.g., 1.63% < 2% → pass)

2025 Error Benchmarks

Field	Excellent	Good	Requires Review
Chemistry Lab	≤1%	1–5%	>5%
Physics Kinematics	≤2%	2–6%	>6%
Mechanical Eng	≤0.5%	0.5–2%	>2%
Clinical Lab	≤3%	3–7%	>7%

📉 Real Examples**:

• g measurement**: 9.65 vs. 9.81 → **1.63%** (Good)
• Density of Al**: 2.68 vs. 2.70 g/cm³ → **0.74%** (Excellent)
• Ohm’s Law**: 12.1 V / 4.1 Ω = 2.95 A vs. 3.00 A → **1.67%** (Good)

How to Use This Calculator

➡️ Percent Error

“Measured g = 9.65 m/s², accepted = 9.81 — % error?” → **1.63%**

➡️ Percent Difference

“Trial 1 = 24.8 cm, Trial 2 = 25.2 cm — diff?” → **1.59%**

➡️ Absolute Error

“Mass: 50.3 g vs. 50.0 g — absolute error?” → **0.3 g**

Note: Uses exact formulas. Handles negative values via absolute value. All outputs rounded appropriately for scientific reporting.