factor in — take into account (when making a decision or calculation)
to include something as an important part of your decision, plan, or calculation, especially when it might affect the result
Say it like a native
Textbook You must take into consideration the cost of postage when calculating the total.
Native Don't forget to factor in postage.
'Factor in' is the natural verb for including something in a calculation; 'take into consideration' is heavier.
Pattern: factor in + noun / factor something in
In use
- When planning your budget, you need to factor in unexpected expenses like car repairs.work
- In my opinion, when choosing a university, students should factor in not just the academic reputation but also the cost of living in that city.IELTS speaking
Common mistake
✗ We need to factor the weather in our plans.
✓ We need to factor the weather into our plans. / factor in the weather.
'Factor X into Y' or 'factor in X' — note the 'into'.
Common collocations
factor in + variable— the cost, travel time, tax, inflation
Don't confuse it
'Factor in' is more specific than 'consider'—it suggests actively including something as part of a calculation or decision, not just thinking about it. It is also more concise and natural in contexts involving numbers, planning, or weighing pros and cons.