Free web calculators
Every number, in one place.
Use these tools in your browser for free, without signing up. Each shows its assumptions. This web collection is separate from the planning tools in the Deco iPhone app.
21 calculators
Retirement & investing
Retirement number
How much to invest each month to retire with the amount you want.
FIRE & Coast FI number
The amount that makes work optional, and the point you can stop investing.
Roth vs Traditional
You deduct at your marginal rate and withdraw at your effective rate. See which wins.
Roth IRA growth
What your contributions become tax-free, and how much of it is growth.
Social Security age
What claiming at 62, 67 or 70 pays you, and which age pays most over a lifetime.
401(k) & employer match
The 2026 limits, and how much free match you are giving up.
Pension calculator
Estimate the pension savings you are on track for.
Dividend income
What your portfolio pays monthly, and what you need for the income you want.
Home, debt & saving
Spending until payday
Reserve upcoming bills and essentials, then see what is left per day.
House options
Compare loan options using dated weekly mortgage benchmarks and editable assumptions.
Home & rent affordability
The house and rent your salary allows, using the 28%, 36% and 30% rules.
50/30/20 budget
The split in your currency, and whether it fits your income and rent.
Debt payoff
How long a card, car or student loan takes, and what the interest really costs.
Savings goal timeline
How long until you reach your savings target at your current contribution rate.
Shared expenses
Compare two-person splits or allocate bills among 3–8 people using equal shares, incomes or agreed weights. Separate reimbursements from unpaid supplier bills.
Bill & reserve planner
Plan first-bill reserves or a continuing fund. In continuing mode, enter final-charge and review dates, inspect funding gaps and download a local calendar.
Cash-flow planner
Plan receipts and payments by date. Compare entered income with uncertain receipts excluded, lowest cash and your chosen buffer, privately in your browser.
Moving budget
Plan unpaid move-in costs, tied-up deposits and savings assigned to moving. Compare them with a separate ongoing household budget using your actual amounts.
Where you stand
Local planning guides
Reference tables
The same maths, worked out in advance for every age, so you can see where you stand before putting a single number in.
Missing the one you need?
Tell me what you are trying to work out and I will build it. Most of the calculators here started as a question someone asked.