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How-to guide

How to Calculate Cone Slant Height: Formula, Steps & Examples

Learn how to calculate Cone Slant Height — the formula explained step by step, with worked examples and a free calculator to check your answer.

By Vikram Iyer, M.Sc Mathematics · Updated Jun 2026 · 2 min read

Calculating your slant height is straightforward once you know the Cone Slant Height formula and what each input means. This guide explains the method in plain language, walks through a manual calculation, and gives worked examples you can follow — then you can do it instantly with the Cone Slant Height Calculator.

What is Cone Slant Height?

The Cone Slant Height calculation tells you your slant height from a few simple inputs. The figure you are solving for here is the slant height.

The Cone Slant Height formula

The core formula is:

Slant height = √(Base radius ^ 2 + Height ^ 2)

Here is what each input means:

  • Base radius — a number. Example: 3.
  • Height — a number. Example: 4.

How to calculate it step by step

  • Write down the base radius (for example, 3).
  • Write down the height (for example, 4).
  • Apply the formula above to get your slant height.
  • Double-check the result with the Cone Slant Height Calculator.

Worked examples

Example 1

Input / OutputValue
Base radius3
Height4
Slant height5.000000

With base radius of 3 and height of 4, the slant height works out to 5.000000.

Example 2

With base radius of 6 and height of 4, the slant height works out to 7.211103.

ResultValue
Slant height7.211103

Example 3

With base radius of 1.5 and height of 4, the slant height works out to 4.272002.

ResultValue
Slant height4.272002

Tips for an accurate result

  • Keep your units consistent — mixing, say, months with years or grams with kilograms is the most common source of error.
  • Round only at the very end. Rounding inputs early can shift the final answer noticeably.
  • Re-run the numbers whenever an input changes, rather than estimating from an old result.

Prefer not to do the maths by hand? — the Cone Slant Height Calculator does it instantly, for free, with the formula and a worked example built in.

Continue exploring math calculators with these tools: Margin of Error Calculator, Sample Size Calculator, Confidence Interval Calculator, Coefficient of Variation Calculator, Regular Heptagon Area Calculator.

Calculators in this guide

Frequently asked questions

The formula is: Slant height = √(Base radius ^ 2 + Height ^ 2). With base radius of 3 and height of 4, the slant height works out to 5.000000.

Gather each input, apply the formula step by step keeping your units consistent, and round only at the end. You can verify your answer instantly with the Cone Slant Height Calculator.

It uses the standard formula with exact arithmetic, so the result is correct for the inputs you enter. Bear in mind that real-world outcomes can still differ when underlying assumptions change.

Vikram Iyer · M.Sc Mathematics

Vikram Iyer is a mathematics educator with over fifteen years of teaching experience, specialising in making quantitative concepts clear and practical for everyday use.