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Pendulum Period Calculator

Calculate a simple pendulum’s period and frequency with a large-amplitude correction.

Used only when “Custom g” is selected.

Period (amplitude-corrected)
2.0102 s
Small-angle period
2.0064 s
Frequency
0.4975 Hz

Step-by-step working

  1. T₀ = 2π√(L/g) = 2π√(1/9.80665) = 2.0064 s
  2. θ₀ = 10° → T ≈ T₀(1 + θ²/16 + 11θ⁴/3072) = 2.0102 s

Mathematical Formula

T₀ = 2π√(L/g); T ≈ T₀(1 + θ₀²/16 + 11θ₀⁴/3072) for amplitude θ₀ in radians.

Overview & Explanation

A pendulum’s period depends on length and gravity; larger swings take slightly longer.

How It Works

  • Compute the small-angle period.
  • Apply the series correction for amplitude.

Practical Applications

  • Clock design.
  • Measuring g in labs.

Example 1: 1 m at 10°

≈ 2.01 s.

1

Inputs

Length (m): 1 · Amplitude (°): 10 · Gravity (body): Earth (9.80665 m/s²)

= entered
2

Step 1

T₀ = 2π√(L/g) = 2π√(1/9.80665) = 2.0064 s

3

Step 2

θ₀ = 10° → T ≈ T₀(1 + θ²/16 + 11θ⁴/3072) = 2.0102 s

4

Period (amplitude-corrected)

Result

= 2.0102 s

Example 2: 0.25 m at 45°

Large swing.

1

Inputs

Length (m): 0.25 · Amplitude (°): 45 · Gravity (body): Earth (9.80665 m/s²)

= entered
2

Step 1

T₀ = 2π√(L/g) = 2π√(0.25/9.80665) = 1.0032 s

3

Step 2

θ₀ = 45° → T ≈ T₀(1 + θ²/16 + 11θ⁴/3072) = 1.0432 s

4

Period (amplitude-corrected)

Result

= 1.0432 s

How it's calculated & sources

T₀ = 2π√(L/g); T ≈ T₀(1 + θ₀²/16 + 11θ₀⁴/3072) for amplitude θ₀ in radians.

Frequently Asked Questions

Does mass matter?
No, for an ideal simple pendulum.
Seconds pendulum?
A ~0.994 m pendulum has a 2 s period on Earth.
How accurate is the correction?
Within 0.1% up to about 60°.