Sizable -

Sizable (adjective)

[sahy-zuh-buhl] / ˈsaɪ zə bəl/

Meaning: fairly large.

Imagine you are working on a project that needs huge amount of efforts. You can say, “This project requires sizable amount of work.”
Sizable can be used for tangible things like,
John has a sizable back yard,
This house has sizable rooms,
The school has a sizable playground.
and also for concepts like,
Sizable efforts,
Sizable portion,
Sizable gains etc…

More examples using Sizable:

A sizable portion of population is still unemployed.
The government promised to allocate a sizable budget to build new universities.
John made a sizable donation to the charity.
This movie has a complex subject, it requires a sizable budget.