Science fair project ideas for kids: 25 testable questions by grade

A good science fair project starts as a question your kid can answer with a number: how far, how long, how many. Below are 25 of them for grades 1 to 8, each one set up so your kid changes one thing and measures one thing. In Kubrio's paper airplane course, your kid folds a plane that flies far, and the question "what made it fly farther?" is already a fair test.

What makes a science fair idea a good one?

A good idea is a question you can test and measure. Science Buddies, the nonprofit that runs a large library of fair projects, says the question should be something you can measure, preferably with a number. It also suggests a simple template: "How does ___ affect ___?" The first blank is the one thing your kid changes. The second is the one thing they measure.

Science Buddies also lists what to steer away from: brand comparisons, surveys of people, and ideas that are hard to control and measure. That is why none of the 25 below ask "which brand is best?" Each one asks about a thing your kid can set up at the kitchen table.

Two more tests before you commit. Can your kid carry on with it for a few weeks, and can they do it safely with what you already have? Science Buddies' advice on finding an idea asks for both.

How do you turn an idea into a fair test?

Change one thing and keep everything else the same. That is what a fair test means, and it is the part judges and teachers look for. Science Buddies' fair test guide uses toy cars as the example: if you give one car a push to start, the comparison is no longer fair.

Here is the recipe, using "Which paper airplane flies farthest?"

1. Name what changes. The wing shape. Try three designs.
2. Name what gets measured. The distance, in steps or centimeters.
3. Name what stays the same. The same paper, the same thrower, the same spot to throw from, the same strength of throw.
4. Repeat it. Throw each plane five times, so one lucky throw doesn't decide the answer.
5. Write it down as you go. A table beats memory.

A fair test also lets your kid be wrong. If the "fancy" plane loses, that is a real result, and a better project than one that went as planned.

Which science fair ideas suit grades 1 and 2?

At this age the science is looking closely and counting. Pick one with a short setup and an answer your kid can see by the end of the week.

1. Which melts an ice cube fastest: the sun, the shade, or the fridge door open on the counter?
2. Which paper towel holds the most water: how many spoonfuls before it drips?
3. How far does a ball roll from the bottom of a ramp when the ramp is higher?
4. Do bigger seeds sprout faster than smaller ones?
5. How many pennies can a foil boat hold before it sinks, with a wide hull versus a narrow one?
6. Does a bubble last longer on a dry hand or a wet hand?
7. Which of five household objects sink, and which float?
8. How does the temperature of the water change how fast sugar disappears into it?

Which science fair ideas suit grades 3 to 5?

By now your kid can run a real fair test, with three versions and five tries each. This is the sweet spot for "easy science fair projects" that still look like science.

1. How does wing shape change how far a paper airplane flies?
2. How does the number of rubber bands change how far a popsicle stick catapult launches a pom-pom?
3. Does the length of a pendulum change how many swings it makes in 20 seconds?
4. How does the amount of baking soda change how high a balloon inflates over a bottle of vinegar?
5. Which paper bridge holds the most pennies: flat, folded, or rolled?
6. How does the angle of a ramp change how far a toy car travels after it?
7. Does a plant grow taller with more hours of light?
8. How does the height of a drop change the size of a splash in a tray of flour?
9. How does the temperature of the water change how fast a tea bag colors it?

Which science fair ideas suit grades 6 to 8?

Older kids can handle more careful measuring and a chart that tells a story. Ask for a prediction first, and for the reason behind it.

1. How does the launch angle of a catapult change the distance it throws? Try five angles.
2. Does adding paper clips to the nose change how far a paper airplane flies, and where is the sweet spot?
3. How does the length of a ruler launcher's arm change how far a paper plane goes?
4. How does salt in water change how many weights a boat can carry before it sinks?
5. Does the tilt of a cardboard sun-shade change how quickly a cup of water warms in the sun?
6. How does the thickness of a rubber band change how far it stretches under the same weight?
7. How does the shape of a parachute change how fast it falls?
8. How does the size of a magnet's contact area change how many paper clips it can hold?

How can you help without doing it for them?

Ask questions, supply materials, and let your kid hold the pen. Science Buddies' advice for parents says a parent's job is to oversee, not to do the experiment for the child. It also says the text on the display board is for the child to write.

There is a good reason to hand the choosing over, too. In a survey of high school students about science fairs, Grinnell, Dalley, and Reisch (2025) found 89.3% positive comments when taking part was optional and 52.6% when it was required, rising to 65.1% when it was required but the student picked their own project. So offer three or four ideas from this list, and let your kid choose.

If your kid gets stuck, ask a question rather than giving an answer. "What would you change first?" and "How will you know?" work better than "Try it this way."

What do you do with a project that goes wrong?

Write down what happened and why you think it did. A plane that crashes, a seed that never sprouts, a measurement that looks odd: these are results too. Ask your kid what they would change on the next try. A project that explains an odd result is often stronger than one where everything went to plan.

If you want a longer read on picking a project your kid will finish, see our article on how to choose a science project at home.

Where can Kubrio help with a science fair project?

Two Kubrio courses fit the lists above, and both end with something your kid made with their hands. In How to make a paper airplane that flies far, your kid folds a plane and learns what makes it fly. In How to make a catapult with popsicle sticks, they build a catapult that launches far. Either one hands your kid a thing to measure and a question about it. If a ruler launcher sounds more fun, there is a course for that too: How to make a paper airplane launcher.

Kubrio is not a fair kit and does not write your kid's report. Your kid builds the thing and runs the test, and the AI crew asks questions along the way instead of giving answers.

What to do at home this week

1. Read the list for your kid's grade, and circle the three questions that make them say "ooh."
2. Let your kid pick one. If they want to change it, change it.
3. Fill in the template together: "How does ___ affect ___?" Write it at the top of a notebook page.
4. List what stays the same, in your kid's words. Aim for at least three things.
5. Run the test five times for each version, and write each number in a table as it happens.
6. Draw a bar chart by hand. Ask your kid what the chart says, then what surprised them.
7. Let your kid write one sentence for each part: the question, what they did, what they found. Fix the spelling only if they ask.

FAQ

What are some easy science fair projects for 3rd grade? Try the paper airplane test, the catapult test, or the ramp and toy car test from the grades 3 to 5 list. Each one uses things already at home and gives a clear number to compare. They also work well for a first fair, because the setup takes about an hour.

How long does a science fair project take? Most take one to two weeks of short sittings. Plant projects need longer, since seeds take days to sprout. Check the fair's deadline first, and work backward so your kid has a spare day for a repeat if something goes wrong.

Can my kid reuse a project idea they found online? Yes, as long as they run the test themselves and report their own results. Many ideas repeat from year to year, so the work that counts is the test your kid actually does. Changing one detail, such as the material or the size, makes it theirs.

Does my kid need a hypothesis? Many fairs ask for one, so check the rules. A hypothesis is a prediction with a reason: "I think the longer wings will fly farther because they catch more air." A prediction that turns out wrong is still a good project.

What if my kid's fair doesn't allow certain materials? Read the rules sheet before buying anything. Most fairs ban live animals, open flames, and anything unsafe. Every question on this list uses ordinary household items, but check with the teacher if you are unsure.