How the math works,
on a $500,000 home.

The figures here rest on a mix of established fact, deliberate assumption, and genuine unknowns. Here's the split up front. The biggest assumption is the rate path: the district committed only to a ceiling (no more than 4¢/year), not a year-by-year plan — so we model the fastest version, meaning these are the most you could be charged in any year, not a forecast.

Indiana taxes the assessed value after homestead deductions, not the market price. For a primary residence, two deductions come off first: a flat $48,000 standard deduction, then a 35% supplemental deduction on what's left.

Nearly $206,000 — about 41% of the home's value — comes off before any school rate applies. That's why the monthly figures land lower than people expect.

⚠︎ Important: the $48,000 / 35% stack used in Steps 1–4 is a fixed reference chosen to isolate the rate change. Under the 2025 law (SEA 1), the standard deduction actually drops to $40,000 in 2027 and phases to $0 by 2031, while the supplemental rises from 40% toward 66.7%. Step 5 shows the real per-year figures — and they change the picture.

The rate is quoted in cents per $100 of assessed value. Turning that into dollars means dividing the rate by 10,000, then multiplying by the net assessed value. Run it at today's 37¢ and at the 57¢ ceiling the ballot authorizes:

Worked out: $293,800 × (57 ÷ 10,000) = $293,800 × 0.0057 = $1,674.66 per year.

To isolate the referendum's cost, compare the bill at the new rate against the bill at the old 37¢ rate in the same year, on the same deductions — changing only the rate. (Steps 1–4 use a fixed deduction stack to keep this clean; Step 5 shows what the real SEA 1 deductions do to the figure.)

This $48.97 is the rate change alone, on the fixed deductions used here. It is not how much more you'll see on your actual bill versus 2026 — because SEA 1 is separately lowering bills over these years. Step 5 untangles the two.

The district committed to raising the rate by no more than 4¢ per year, capping at 57¢. The table below shows the fastest allowed path — +4¢/year until it hits the cap in 2031, then flat. (This walkthrough holds the fixed deductions from Steps 1–3; Step 5 layers in the real SEA 1 deduction changes.)

"Ref. cost/mo" is the rate change measured the honest way — that year's rate vs the old 37¢ rate, on the same value. The rate reaches the 57¢ cap in 2031 (shaded) and holds flat after. The district could phase in more slowly than 4¢/year, which would lower the early-year figures; they committed only to the 4¢ ceiling.

Steps 1–4 used a single fixed deduction stack to keep the rate math clean. But the same 2025 law that prompted this referendum — Senate Enrolled Act 1 — is rewriting the homestead deductions every year across exactly the referendum window. The standard deduction shrinks from $48,000 toward $0 by 2031, while the supplemental deduction climbs from 40% toward 66.7%. Those two moves lower your total school-tax bill — independently of the referendum.

This is where the two questions split apart. The table below shows your total bill falling under SEA 1, alongside the referendum's own cost — the rate change measured the honest way, 57¢ vs 37¢ on the same year's value. The deductions lower the bill; they do not make the referendum free. Drag the slider to also let the home's assessed value grow.

This is the one place that involves any forecast — only the value-growth slider. The deduction schedule itself is statutory (IC 6-1.1-12-37 and 37.5, as amended by SEA 1), not a guess.

Two distinct things are shown. The total bill falls under SEA 1 because the growing deductions shrink the taxable base — but that relief happens regardless of the referendum. The referendum cost column (right) is the rate change in isolation: 57¢ vs 37¢ on the same year's value, which is what the referendum actually charges you (~$28/mo at the cap on this $500k home). The deductions don't reduce the referendum's cost — they reduce the bill it sits inside. (A separate $300 homestead credit, applied to the whole bill after the rate, isn't shown here.)

• Referendum dollars skip the cap. Voter-approved referendum levies are exempt from Indiana's 1% circuit-breaker cap and get no income-tax replacement credit, so this portion of a bill is felt in full.
• The deductions move every year. Steps 1–4 hold a fixed deduction stack to isolate the rate, but SEA 1 phases the standard deduction to $0 by 2031 and the supplemental up to 66.7%. Step 5 applies the real schedule: it lowers your total bill, but the referendum's own cost (the same-year rate delta) still grows toward ~$28/mo at the cap on this $500k home.
• SEA 1's $300 homestead credit lives elsewhere. The 2025 law's new credit (10% of the bill, capped at $300) is subtracted from the whole tax bill after the rate, not from the referendum slice, so it isn't shown in these referendum-only figures.
• Rate path is the fastest allowed, not modeled middle steps. The 37¢ and 57¢ endpoints are firm and the deduction schedule is statutory; the year-by-year path is the fastest the district committed to (+4¢/yr to the cap in 2031), which they could undershoot. Any assessment-growth assumption is the only forecast.

Here's a catch worth knowing: your Indiana tax statement (form TS-1) does not print a line that says "operating referendum." The school taxes appear bundled, so people looking to verify their own number often can't find it. Here's where it actually hides.

The school taxes split into separate pieces. In Table 3 (the breakdown of where your taxes go), the school's share shows up as a "School District" line and a "School (Debt)" line — but the operating referendum is folded into the School District line, not itemized on its own. For Noblesville Schools, the certified 2025-pay-2026 rates are:

Note these are two different things. The 37¢ operating referendum is the one on November's ballot and the one this site models. The 8¢ referendum debt is an older, separate voter-approved construction-bond levy that is not on the ballot and runs through 2032.

Where the dollar amount shows up. The cleanest place to see the combined referendum on your bill is Table 2 (the property-tax-cap section), on the line "Upward adjustment due to voter-approved projects and charges (e.g., referendum)." That figure is your total referendum levy — both pieces — because referendum charges sit above the 1% cap. On a real Noblesville bill with $310,080 net assessed value, that line reads $1,395.36, which is exactly the 0.4500 total rate × the net value. The operating-referendum portion of that is 37/45 of it, about $1,147.

So if you want to check this site's estimate against your own bill: the "referendum" you see in Table 2 includes the 8¢ debt levy, so it runs higher than the operating referendum alone. Subtract the debt portion (8/45 of the Table 2 figure) to isolate the operating referendum this site is about. You can confirm the certified rates yourself in the Hamilton County Auditor's 2026 School Referendum Rates document.