Moderate
In development · Early access open
The numbers behind the homes you love.
Paste a home you're considering. MortgageMath shows what it really costs each month, how much cash you'll have left after closing, and how it stacks up against the rest of your shortlist.
Free to join. No lender calls, ever. We never sell your email. See how it works ↓
Income $138kSaved $82kRate 6.50%Down 10%
Moderate
Comfortable
The gap
Listing sites answer "what's the payment?" You're asking much bigger questions.
$429,000
Est. payment $2,440/mo
principal & interest, default assumptions
principal & interest, default assumptions
$3,572/mo
Same house with tax, insurance, PMI and upkeep added, for an example buyer putting 10% down.
- How much cash will I have left after closing?The down payment is only part of what leaves your account.
- What will this house really cost every month?Tax, insurance, PMI, HOA and upkeep included.
- How does 5% down compare with 10% or 20%?Monthly cost, cash on hand and when PMI ends.
- Does the cheaper house actually cost less?A lower price can hide a higher tax bill or an HOA.
- Can I qualify and still end up house-poor?What a lender approves and what feels comfortable can differ.
- Which home on my list is financially strongest?Side by side, on the same assumptions.
How it works
Paste a listing. See the financial reality behind it.
Set up your profile once: income, debts, savings and credit range. Every home you add is measured against it.
1 · Add a home
Or type the price, taxes and HOA yourself. It takes about 10 seconds.
2 · Facts get organized
- Asking price$389,000 Sourced
- Property tax$5,600/yr Sourced
- HOANone Sourced
- Insurance$1,600/yr Estimate
- Upkeep1.5%/yr Assumption
3 · Know what it means for you
Example data
118 Old Mill Rd
3 bd · 2 ba · 1,920 sq ft · built 1910$3,445Monthly ownership cost
$50,570Cash to close
$4,505Left each month
- Lowest monthly cost on your list, even with a higher upkeep allowance for a 1910 house.
- PMI of $146/mo is scheduled to drop off after about 9 years.
- Leaves $31,430 in savings after closing, above your $30,000 target.
Link import will work where listing data is available. Manual entry always works.
Your shortlist
Every home you're considering, with the numbers that matter up front.
Save homes as you tour them. Each card leads with what it costs you, not just what it costs.
Example buyer: $138,000 household income, $82,000 saved, 10% down at 6.50%.
Compare 3 homes →
Compare homes
The listing price is one number. The decision takes about ten.
Line up the homes on your list using the same assumptions, and the relationships hidden behind the asking prices show up.
| Example dataGreen = best on the list | 27 Pine Ridge Rd |
14 Harbor View Ln |
118 Old Mill Rd |
|---|---|---|---|
| Purchase price | $429,000 | $403,000 | $389,000 |
| Est. monthly cost | $3,572 | $3,589 | $3,445 |
| Cash to close | $55,770 | $52,390 | $50,570 |
| Cash remaining | $26,230 | $29,610 | $31,430 |
| Property tax | $492/mo | $617/mo | $467/mo |
| HOA | $0 | $285/mo | $0 |
| Est. maintenance | $358/mo | $168/moHOA covers exterior | $486/mo1910 house |
| Housing % of income | 27.9% | 29.7% | 25.7% |
| Monthly cash remaining | $4,378 | $4,361 | $4,505 |
| 5-year costexcluding equity built | $202,500 | $204,200 | $196,000 |
27 Pine Ridge Rd · three ways to finance it
Same house, same rate, different down payments
5% DOWN$3,757/mo
- Cash to close
- $34,320
- Left after
- $47,680
10% DOWN$3,572/mo
- Cash to close
- $55,770
- Left after
- $26,230
20% DOWN$3,140/mo
- Cash to close
- $98,670
- Left after
- −$16,670
Two different questions
What a lender will approve and what fits your life are not the same number.
MortgageMath shows both side by side, so a yes from the bank doesn't get mistaken for a comfortable budget.
Could you likely finance it?
Likely: Yes27 Pine Ridge Rd · example
Debt-to-income (back-end)31.9%
0%~45% common limit60%
Based on standard lending ratios. MortgageMath doesn't make lending decisions. Only a lender can approve a loan.
Does it fit the life you want?
Fit: ModerateAgainst your own targets
Savings left after closing$26,230
$0Your target $30k$50k
Left each month after housing, upkeep, debts$4,378
$0Your floor $3.5k$6k
You set the targets: how much cushion you want, and how much you want left each month for everything else.
27 Pine Ridge Rd · monthly
$3,572- Principal & interest6.50% · 30 yr · $386,100 loanYour input$2,440
- Property tax$5,900/yr from tax historySourced$492
- Homeowners insurance$1,450/yr regional estimateEstimate$121
- PMI0.50%/yr at 720–739 credit · ends after ~9 yrsEstimate$161
- HOAnone listedSourced$0
- Maintenance1% of price per yearAssumption$358
Illustrative example. Replace any estimate with a real quote and every home recalculates.
Transparency
No mystery score. Show the math.
Every number says where it came from. Open it, check it, change it.
Sourced
Sourced property data
Pulled from the listing or public records, like price, tax history and HOA.
Your input
Your inputs
What you tell it: rate quote, down payment, income, debts.
Estimate
Estimates
Reasonable defaults for things like insurance and PMI until you have a real quote.
Assumption
Model assumptions
Rules of thumb, like a maintenance allowance, stated plainly and adjustable.
Planned feature
When a listing changes, see what it does to your numbers.
A price drop is news. What it means for your monthly cost and your cash at closing is the part you need.
Coming after launch
-
$15,000 price drop2h ago118 Old Mill Rd · $389,000 → $374,000Monthly cost −$109Cash to close −$1,950
-
Under contractYesterday14 Harbor View LnMoved to "watching." Your comparison updates to 2 homes.
-
Back on market3 days ago14 Harbor View LnRestored to your shortlist with current numbers.
-
Property tax updatedLast week27 Pine Ridge Rd · $5,900 → $6,250/yrMonthly cost +$29
Why this exists
Built because I wanted this myself.
I'm not a realtor or mortgage broker. I'm an engineer trying to buy my first home.
When I started looking, the numbers I actually wanted weren't in one place. Mortgage calculators could estimate a payment. Listing sites could show me homes. I wanted to see what buying each house would do to my finances, and compare those decisions side by side.
So I started building MortgageMath. It isn't tied to any sale, loan or commission. It just shows the math.
Early access
Buying a home is complicated. The math shouldn't be.
MortgageMath is being built now. Join the early-access list to follow development and be among the first to try it.
One email when early access opens, plus occasional build updates. Unsubscribe anytime. Privacy