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Pendulum period calculator

Compute the swing period of a simple pendulum from its length (T = 2π√(L/g)).

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Enter Length (m), Gravity (m/s²) and the Pendulum period calculator works out Period (seconds) straight away. For instance, with Length (m) = 1 and Gravity (m/s²) = 9.81 it returns Period (seconds) = 2.006.

How to use it

  1. Enter your values: Length (m), Gravity (m/s²).
  2. Read the result instantly: Period (seconds).

Frequently asked questions

What does the Pendulum period calculator actually compute?

It takes Length (m) and Gravity (m/s²) and derives Period (seconds) from them. The calculation is live as you type, so the result updates on every change.

What information do I need to provide?

2 values: Length (m) and Gravity (m/s²). Nothing else is required — no account, no file upload.

Can you show a worked example?

With Length (m) = 1 and Gravity (m/s²) = 9.81, the calculator returns Period (seconds) = 2.006. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

What happens if I enter larger values?

It moves a lot. Using Length (m) = 1.1 and Gravity (m/s²) = 19.62 instead, Period (seconds) goes from 2.006 to 1.488 — which is why it is worth testing a few scenarios rather than trusting a single figure.

What does it give for smaller values?

Scaled down to Length (m) = 0.9 and Gravity (m/s²) = 4.91, Period (seconds) comes out at 2.69. The relationship is worth checking at both ends before you rely on a single result.

When would I actually use this?

Checking a homework answer, sizing something before building it, and getting an order of magnitude before committing to a design — a torque on a bolt, the force a spring returns, the frequency a circuit resonates at, how long light takes to arrive.

What is the most common mistake?

Feeding in a value in the wrong unit. Physics formulas assume SI throughout, so grams instead of kilograms or centimetres instead of metres shifts the answer by powers of ten without any warning.

What is the difference between the Pendulum period calculator and the Frequency & period calculator?

This one returns Period (seconds); the Frequency & period calculator returns Period (s) and Period (ms). That is the whole difference — open the one whose figure you need.

Is there a tool for the next step?

Orbital period calculator is the closest one after this: Compute how long an object takes to orbit a body from the orbit radius and mass.

What else is worth having open alongside it?

Free fall calculator and Potential energy calculator — they come up in the same task often enough to be worth a second tab.

Further reading

All guides →
ExplainerHow the Doppler Effect Works: The Formula, the Sign Convention, and Why Moving the Source Is Not the Same as Moving the ListenerFor sound, f' = f(v + v_o)/(v − v_s) — and getting the signs backwards is the classic error. Here is the convention spelled out, a 440 Hz source computed at four speeds, and why light needs a different equation entirely.ExplainerHow Buoyancy Works: Archimedes' Principle, and Why Ice Floats With 10.5 % Above WaterThe upward force equals the weight of the fluid pushed aside. That one sentence decides whether something floats, and if it floats, exactly how much of it stays under.GuideThe Four Kinematics Equations: Which One to Use, and What Each One Leaves OutFive variables, four equations, and each equation is missing exactly one of them. Choose by looking at the variable the question never mentions.ExplainerProjectile Motion Explained: Range, Height, Flight Time — and Why 45° Is Not Always BestThree formulas cover the whole of projectile motion on level ground. The catch is level ground: the moment launch and landing heights differ, the 45° result stops being true.ExplainerWhat Is the Reynolds Number? The Formula, the Units That Cancel, and Why 2 300 Is Only for PipesRe = ρvL/μ compares inertia with viscosity, and the units really do cancel. See the number worked out for honey, a household pipe, an artery, a swimmer and a wing — and why the 2 300 threshold belongs to pipe flow alone.ExplainerHooke's Law Explained: F = kx, Real Spring Constants, and Where It Stops HoldingHooke's law says force is proportional to stretch — but only below the elastic limit. Here is F = kx with worked numbers, what a 200 N/m spring actually feels like, and how springs combine.