Savings rate, explained
Your savings rate is the portion of your income that you keep rather than spend. Of all the personal-finance ratios, it has the most direct bearing on how fast net worth grows.
The calculation
Savings rate = (income − spending) ÷ income.
Earn $6,000 a month and spend $4,500, and the savings rate is 25%.
Choose a consistent definition
Use after-tax income, or pre-tax, but not both. Decide whether employer retirement contributions count. The specific choice matters less than applying it the same way every month.
Why it matters
Two forces move net worth: what your investments earn and what you add. Early on, the second dominates. A higher savings rate raises net worth faster than any marginal improvement in returns.
Expect variation
Bonuses, annual bills and travel make any single month unrepresentative. A trailing twelve month figure is steadier.
Savings rate and projection
Your savings rate, combined with the interest your accounts pay, allows a reasonable projection of where your net worth goes if nothing changes. MizuFlow shows that projection from your own linked accounts, not a generic assumption.