Measure the Sun's Size

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In this activity, learners make their own pinhole viewer in order to measure the size of the sun. After using the viewer to project circular image of the Sun on paper, learners use ratios and an equation to calculate the Sun's real size. Step-by-step instructions are included with photos along with important safety guidelines. This activity needs a sunny day, however an alternative is provided using the light from a tablet in a dark room. Activity guide includes a helpful section on the required equation and variables, and a "What's going on?" explanation on how the pinhole viewer works.

Quick Guide

Preparation Time:
5 to 10 minutes

Learning Time:
10 to 30 minutes

Estimated Materials Cost:
$1 - $5 per group of students

Age Range:
Ages 8 - adult

Resource Type:


Materials List (per group of students)

  • sheet of cardboard (like from a cereal box)
  • piece of white paper
  • small piece of aluminum foil (about 3 cm x 3 cm)
  • pin or thumbtack
  • scissors
  • tape
  • ruler
  • string or yarn (about 60 cm long)
  • hardcover book (optional)


  • Earth and Space Science
    • Solar System
      • The Sun
  • Mathematics
    • Algebra
      • Equations and Inequalities
    • Measurement
      • Size and Scale

Informal Categories

  • Outdoor Activity


To use this activity, learners need to:

  • see

Learning styles supported:

  • Involves hands-on or lab activities


This resource is part of:

Access Rights:

  • Free access


Source Collection

  • DIY Science App


  • , The Regents of the University of California, 2014

Funding Source:

  • NASA, NNX10AE05G