Budget calculator — free online tool
The budget calculator is a free browser tool that takes your monthly income, fixed costs and desired savings rate and calculates a safe spending limit per day and per week. Everything runs in your browser; no data is sent anywhere.
The calculator uses a flexible 50/30/20 rule: fixed costs first, then the savings share, and the remainder is divided by the days in the period. The formulas match the budget tracker template — the result can be carried over in one row.
If the daily limit looks too tight, lower the savings rate or revisit the fixed-cost block — forgotten subscriptions usually live there.