Savings rate is a descriptive ratio:
savings included in your definition ÷ income included in your definition
State whether income is gross or take-home and whether employer retirement contributions, debt principal and irregular income are included. Otherwise two households can report different rates from the same cash flows.
There is no universal 20% target or one budgeting split that fits every household. Income stability, housing costs, debt, dependants, benefits and goals all matter. Compare your own ratio consistently through time and connect it to the contribution required by specific goals.
A lower rate can identify limited current room; a higher rate does not by itself prove that protection, liquidity or goals are adequately funded. The ratio is a starting point for review, not a verdict.