Martha's Vineyard is about 4.2 times bigger than Manhattan.

Manhattan is approximately 55 km² (21 sq mi), while Martha's Vineyard is approximately 227 km² (87 sq mi), making Martha's Vineyard 315% larger than Manhattan.
Tip: This to-scale comparison of Manhattan vs. Martha's Vineyard uses the Mercator projection, which distorts the size of regions near the poles.
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