Rectangle Area Worksheets for Grade 3 (Free PDF With Answers)
October 20, 2026
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Finding the area of a rectangle in 3rd grade comes down to one formula: length times width. The free worksheet below has 5 practice problems in centimeters with a full answer key — download it, then use the explanation and worked example below if your child or student needs the formula explained before they start.
The formula
Area of a rectangle = length × width. If a rectangle is 8 cm long and 5 cm wide, its area is 8 × 5 = 40 square centimeters, written 40 cm². The unit is always squared — cm², not cm — because area measures a flat surface, not a distance.
Worked example
Take a rectangle that measures 10 cm by 7 cm:
- Multiply the two side lengths: 10 × 7 = 70.
- Add the squared unit: 70 cm².
That's the whole process. The free worksheet uses the same format with five rectangles of different sizes, from 6 cm × 4 cm up to 19 cm × 17 cm, so a student practices the same multiplication step at a few different difficulty levels.
Common mistakes
- Forgetting the squared unit. Writing "40 cm" instead of "40 cm²" is the single most common error graders see — it's a quick habit to check for every time.
- Adding instead of multiplying. A student who isn't yet confident with multiplication sometimes adds the two sides (8 + 5 = 13) instead of multiplying. If this shows up, it's worth reviewing multiplication facts before more area practice.
- Mixing up area and perimeter. Area is the space inside the rectangle (length × width); perimeter is the distance around it (add all four sides). If a student's answer looks too small for the numbers given, check whether they added the sides instead of multiplying them.
Get more practice
This worksheet is one of five in the Grade 3 Shapes Worksheets pack, each with its own answer key and a fresh set of rectangles to practice on. If you want every grade from Kindergarten through Grade 4 — shape recognition, perimeter, area, and triangles — the K-4 Shapes Worksheets Bundle covers all five grade packs in one download.
More to explore
Grade 3 Shapes Worksheets — Area
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K–4 Shapes Worksheets Bundle — 15 Printable Worksheets
5 grades · 15 worksheets · answer keys includedFAQ
What is the formula for the area of a rectangle?
Length times width. For an 8 cm by 5 cm rectangle, the area is 8 × 5 = 40 cm².
Why is the answer in cm² and not cm?
Area measures a flat surface, so the unit is squared. A length is measured in cm; an area is measured in cm² (square centimeters).
What's the difference between area and perimeter?
Area is the space inside a shape (length × width for a rectangle). Perimeter is the distance around the outside (the sum of all four sides).
Does the full pack cover perimeter too?
This particular worksheet focuses on rectangle area. The Grade 3 Shapes pack builds on the perimeter skills introduced in Grade 2 and leads into area, matching the typical grade-3 scope.
Is an answer key included?
Yes, every worksheet — the free download and the full pack — comes with a matching answer key.