You do not need a suite to do the math
DIY landlords do not lose money because they lacked a 40-feature dashboard. They lose it on a late-fee clause nobody checked against the state cap, a mid-month move-in priced by vibes, a vacancy that "was only two weeks" until cleaning and locksmiths showed up, and a depreciation deduction that never got set up because no check cleared.
These 10 free tools are Manor Keeper calculators. They do not list your unit on Zillow, screen a tenant, or file your taxes. They make the number in front of you honest before you put it in a lease, a listing, or a Schedule E packet.
Use them as a stack, not a buffet. Leasing math first. Then vacancy and reserves. Then tax and return math. The full calculator index has more than these ten; these are the ones that earn a bookmark in 2026.
The calculators are estimates. State caps change. Lenders invent overlays. Your CPA still owns basis and passive-loss judgment. When a number will live in a lease or a tax return, confirm it.
1. Late fee calculator for landlords
A lease that says "10% plus $10 a day" is not automatically lawful, and it is not automatically what you should book. Many states — and some cities — cap late fees or require a grace period.
The late fee calculator takes monthly rent, days late, and state. It estimates a daily-style fee and flags when a common state cap would reduce it. That is a starting point for "what might I charge," not a signed opinion letter.
Use it when you write the clause, not when you are already mad in month four. Then record what you actually charged and collected. Late fees you never received are not Schedule E income on the cash method. The books version is late fees on Schedule E.
2. Prorated rent calculator
January 15 move-in. Is first rent $1,800 or half? Landlords fight with themselves over 30-day months, 31-day months, and whether move-in counts as a full day.
The prorated rent calculator needs monthly rent and the move-in date. It returns the first-month amount so you and the tenant are staring at the same number before keys change hands.
Put the method in the lease ("daily rate based on days in the month") so you are not renegotiating arithmetic at the door. The same math shows up at move-out if rent is due through a mid-month date. Guessing in a text thread is how deposits get messy.
3. Income-to-rent (3×) calculator
"They seem nice" is not a screening policy. Most small landlords use an income multiple — often 3× monthly rent in gross income — as a first filter, then verify.
The income-to-rent calculator turns rent into the annual income target at 2.5×, 3×, and 3.5×. Optionally enter what the applicant actually earns and see whether they clear the bar.
Use it to write the criterion before you look at applications, then apply it the same way to everyone. Fair housing cares about consistency. Fake pay stubs still exist; the calculator does not catch those. Pair it with how rental applications and screening actually work and, when you are ready for a system, rental applications.
4. Rent increase calculator
Renewal season is where DIY landlords either underprice out of guilt or overcorrect after one podcast. You need the new rent, the annual dollar change, and a sentence you can put in a letter.
The rent increase calculator takes current rent and either a percentage or a CPI-style input and shows the new amount plus the yearly delta.
Run it next to actual comps, not next to hope. A 5% bump on a unit already above every listing within a mile is how you buy a vacancy. The letter side is raise rent at renewal; the market side is pricing with rent comps.
5. Vacancy cost calculator
"It's only two weeks empty" ignores make-ready. Lost rent plus cleaning, paint, lock changes, listing fees, and vacant-unit utilities is the real invoice.
The vacancy cost calculator asks for monthly rent, vacancy length in weeks, and turnover costs. It returns total cost, plus cost per day, so you can see whether $200 of better photos is cheaper than three extra empty days.
Use it when a tenant gives notice — not after you have already taken a leisurely month to pick a paint color. Speed is a financial decision. See how to use the vacancy cost calculator for the worked example.
6. Maintenance reserve calculator
Cash flow that assumes nothing ever breaks is fan fiction. Roofs, HVAC, and turnovers arrive as lumps. A monthly reserve is how those lumps do not become credit-card panic.
The maintenance reserve calculator uses the 1% rule (about 1% of property value per year) or a 50-cents-per-square-foot rule if you enter footage.
It is a planning number, not a tax category. The reserve itself is not a Schedule E deduction. The repair you eventually pay from the reserve is. Keep the reserve in the rental account so you can see it; do not hide it in a vacation fund. Broader cash-cushion thinking: rental property cash reserves.
7. Residential rental depreciation calculator
Depreciation is the deduction that requires no check. Residential rental buildings (not land) depreciate over 27.5 years. Skipping it does not make the building immortal. When you sell, recapture can still look at depreciation allowed or allowable.
The depreciation calculator needs purchase price and land value. It estimates the annual Schedule E line 18 slice.
Land vs building is the input people fake. Closing statements and tax assessments are starting points; your CPA owns the allocation. If you have never taken depreciation, that is a catch-up conversation (amended return or Form 3115), not a DIY Form 4562 at midnight. Sale-side: depreciation recapture.
8. Passive loss / rental loss deduction checker
A paper loss on Schedule E does not automatically cut your W-2. Rental activity is usually passive. There is a $25,000 special allowance for many active small landlords, and it phases out as AGI climbs from $100,000 to $150,000 (those thresholds are the classic ones — confirm current law with your CPA).
The passive loss checker takes AGI and the passive loss and shows how much might be deductible this year versus suspended.
Use it so you do not spend the paper loss twice in your head — once as "tax savings" and once as "the house is losing money." The rules write-up is rental income and passive activity loss.
9. Rental ROI / cash-on-cash calculator
Cap rate ignores your loan. Cash-on-cash return does not. DIY landlords mix them up, then buy a house that looks like a 7% cap and feels like a $600 monthly subsidy.
The rental ROI calculator wants purchase details, rent, and expenses. It organizes cash flow, cash-on-cash, cap rate, and a holding-period story.
Trust it for structured thinking. Override it for vacancy lumps, real insurance quotes, and the fact that appreciation is not a salary. Walkthrough: how to use the rental ROI calculator. If you already own the place, actual books beat a calculator you re-type every quarter.
10. Cash flow calculator
ROI is a story about returns. Cash flow is whether the checking account survives this month. Mortgage, taxes, insurance, maintenance, vacancy, and (if you ever hire one) management fees all leave before "profit" arrives.
The cash flow calculator starts from monthly rent and subtracts those operating pieces. Use it when a listing looks cheap until you add a realistic vacancy and a maintenance line.
If the result is negative, that is information, not a moral failure. Some landlords subsidize a house for other reasons. Pretending the mortgage is the only expense is how people are surprised in February. Pair it with the cap rate calculator when you are comparing properties, and with expense tracking when you want last month's real number instead of a model.
Use them as a year, not as a dare
A sane 2026 loop:
- New lease: prorated rent, income-to-rent bar, late-fee clause checked against the calculator.
- Notice given: vacancy cost before you slow-walk the make-ready.
- Renewal: rent increase next to comps, not next to inflation folklore.
- Every month: cash flow vs the bank; maintenance reserve still funded.
- Tax season: depreciation estimate, passive-loss check, then a packet — sample Schedule E and the tax prep checklist.
If you hold title in a partnership or S corp, the packet costume is Form 8825, not Schedule E. The calculators do not care. The form does.
Browse everything on the calculators page. When you want the year categorized while it happens — not reconstructed — Manor Keeper is the ledger next to the math.
Keep the math, then keep the books
Manor Keeper is for DIY landlords who list, lease, and keep their own books. The calculators stay free. The ledger is free for up to 3 units, or start a 14-day Pro trial with no credit card for bank import, receipts, and a Schedule E / Form 8825 worksheet. See pricing.
You might also like:
- Free landlord calculators for rent, leases, and taxes
- How to track rental property expenses for taxes — a beginner's guide
- Schedule E vs Form 8825: what landlords need to know
- Late fee calculator for landlords
- The DIY Landlord's Tax Prep Checklist
- Sample Schedule E for a DIY landlord rental
- Schedule E reports for landlords