About
Free calculators for everyday property management math.
Who it's for
Property managers, landlords, leasing staff, and renters who need a number they can stand behind and a clear record of how it was reached. Each calculator shows the math step by step and can copy the result for an email, a ledger note, or a resident.
There's no account to create, and the calculators run entirely in your browser. See the privacy page for details. To ask a question, report a problem, or suggest a calculator, use the contact form.
How the math works
Amounts are handled in whole cents, so results don't pick up the small rounding errors that ordinary decimal math can introduce. Fractions stay exact until the final step, then round to the nearest cent, and half a cent rounds up. For a mid-month rent change, each part is rounded separately so the parts add up exactly to the total.
If you type more decimal places than a calculator uses, dollar amounts are rounded to the nearest cent and percentages to two decimal places before the calculation runs, with halves rounding up.
Calculators that prorate by day let you choose between the actual number of days in the month and a 30-day accounting month. Use the method your lease or company policy specifies.
What these tools don't do
They calculate the figures you enter. They don't tell you what a lease requires, what local law allows, or whether a charge is appropriate. All amounts are in US dollars.
Method details
Each calculator page explains its formula and includes a worked example.