Loan margin calculator

Type the loan amount, the reference rate, the margin, and the term in years. The calculator adds the rate and computes an annuity payment. 5.75% plus 2.00% is 7.75%. On 400,000 over 25 years the margin share is about 26%. We do not fetch a market index.

Rate = index + margin, then an annuity. You type the index from an offer. No live quotes. A cost sketch, not a tracker. Bare product: margin × amount.

Input data

Additional options (fees and Scenario B)

Scenario B - fill any B field to compare. Empty B fields inherit A (except margin, when margin B is set).

Result

Loan amount, Reference / base rate (% p.a.), Lender margin (% p.a.) and Term (years). The result shows up here.

How results are calculated

Loan margin adds Reference / base rate (% p.a.) to Lender margin (% p.a.) and only then builds an annuity, the equal installment. 5.75 plus 2.00 = 7.75%. The margin share is 2.00 / 7.75, about 25.8%, about 26% on the page. At Loan amount 400,000 and Term 25 years the payment at 7.75% is 3,021.32. Bare 400,000 × 2% = 8,000 lives on margin times amount and is not a payment.

People compare two margins at the same SOFR or EURIBOR. You type the index from an offer. The calculator does not fetch a quote. Scenario A at a 5.75% base and a 1.8% margin is a 7.55% rate and a 2,968.99 payment. Scenario B at a 2.3% margin is 8.05% and 3,100.53. The payment gap is about 132. In the example with fees, all-in drifts by about 39,500 over 25 years. Custom total rate A overrides the sum of base and margin when you type it.

Required fields are Loan amount, Reference / base rate (% p.a.), Lender margin (% p.a.), and Term (years). Optional: Origination / upfront fee, Monthly fee, Custom total rate A, and the Scenario B set. Interest is the payment total minus principal. All-in adds origination and the monthly fee times months. At 300,000, a 5% base, 30 years, A margin 2.5% and B margin 1.9% plus origination 3,500, the lower B margin still wins all-in despite the fee.

Total cost of loan starts from a ready 11% rate and a 1,087.12 payment. Simplified APR, the annual percentage rate, is a power of cost. This calculator stays with building a rate. Header currency only labels the amounts. A comma and a period in 5.75 mean the same index.

The calculator waits for a positive amount, a non-negative base and margin, and a term. This is a sketch at a fixed combined rate, not live quotes and not a credit decision. Tomorrow’s index in an offer may differ from the 5.75 you type.

Type 400,000, 5.75, 2.00, and 25, click Calculate, and check 7.75% and about 26%. Then try A 1.8 and B 2.3 to see payments 2,968.99 and 3,100.53.

How to use

  1. Type Loan amount, for example 400,000, Reference / base rate (% p.a.), for example 5.75, Lender margin (% p.a.), for example 2.00, and Term (years), for example 25.
  2. Optionally add Origination / upfront fee and Monthly fee. Custom total rate A overrides the sum of base and margin.
  3. Fill Scenario B when you want a second margin or a second index at the same amount.
  4. Click Calculate. 5.75 + 2.00 = 7.75%, margin share about 26%, payment on 400,000 over 25 years 3,021.32.
  5. Bare 400,000 × 2% = 8,000 lives on margin times amount. All-in from a ready rate lives on total cost of loan.

Lender margin plus the reference rate

Rate = index + margin, then an annuity. 5.75% plus 2.00% is 7.75%. On 400,000 over 25 years the margin share is about 26%.

margin
Lender margin added to the index. 2.00 on a 5.75 base is a 7.75 rate and about a 26% margin share on 400,000 / 25 years.
Reference
The index from an offer, Reference / base rate. 5.75 + 2.00 = 7.75. The calculator does not fetch live quotes.
margin share
How much of the combined rate is margin. 2.00 of 7.75 is about 26%. Half a point on scenario B adds about 132 to the payment.

Usage examples

Example 1

  • Amount 400,000, 25 years
  • Base 5.75% + margin 2.00%

Rate 7.75%
Margin share ≈ 26%

5.75 + 2.00 = 7.75. Margin is about a quarter of the combined rate.

Example 2

  • 400,000, base 5.75%, 25 years
  • A: margin 1.8% + fees
  • B: margin 2.3%

Δ payment ≈ +132/mo.
Δ all-in ≈ +39,500

Half a percentage point of margin adds up over a long term.

Example 3

  • 300,000, base 5%, 30 years
  • A: margin 2.5%
  • B: margin 1.9% + origination 3,500

B cheaper all-in
despite the fee

A lower margin often beats a higher upfront fee over a long term - compare all-in.

Example 4

  • 300,000
  • 20 years
  • Base 5.50% + margin 1.80%

Rate 7.30%
Payment 2,380.22

What payment is 300,000 over 20 years at 5.50% plus a 1.80% margin? Rate 7.30%, Payment 2,380.22.

Example 5

  • 400,000
  • 25 years
  • Base 5.75% + margin 1.60%

Rate 7.35%
Payment 2,917.05

What payment is 400,000 over 25 years at 5.75% plus a 1.60% margin? Rate 7.35%, Payment 2,917.05.

How to interpret the result

  • The result shows how base rate + lender margin translates into the nominal rate, instalment, and total cost in a simplified model.
  • It is a useful way to see how even a small margin change can affect the monthly payment and long-term cost.
  • It is not a statutory APR tool or a live market-rate tracker - it is meant to compare how sensitive an offer is to margin changes.

When to choose another tool

  • Educational “margin × principal” sketch → Cost of loan margin sketch
  • Fuller total-offer cost view → Total cost of loan
  • Annual cost percentage style estimate → APR estimate

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FAQ

What rate at a 5.75% index and a 2.00% margin?

7.75%. Margin share 2 / 7.75 ≈ 25.8%, about 26% on the page. The payment on 400,000 over 25 years is 3,021.32.

What is the payment gap from 1.8% versus 2.3% at a 5.75% base?

About 132. 7.55% is 2,968.99, 8.05% is 3,100.53. In the example with fees, all-in drifts by about 39,500.

Is 400,000 × 2% the same number as payment 3,021.32?

No. 8,000 is the product on margin times amount. 3,021.32 is the annuity from the full 7.75% rate over 25 years.

Does the calculator fetch SOFR or EURIBOR?

No. You type Reference / base rate from an offer. No live quotes. Tomorrow’s index may differ from 5.75.

What does Custom total rate A do?

It overrides the sum of base and margin. If you type 7.00, the payment uses 7.00, not 5.75 + 2.00.

When does B with a 3,500 fee still win?

At 300,000, a 5% base, and 30 years, a 1.9% margin versus 2.5% eats the 3,500 on all-in. The payment drop outweighs the one-time fee.

Is this statutory APR?

No. APR, the annual percentage rate, in the simplified version is a sibling page. Here you build a rate and a payment.

Does a comma in 5.75 work?

Yes. 5,75 and 5.75 are the same index. Header currency only labels the amounts.

Do I have to fill Scenario B?

No. Without B you see rate, margin share, payment, and all-in for one offer.

Is 7.75% a credit decision?

No. It is the sum of two typed percents and a payment sketch. An offer may change the margin after a promo window.

Knowledge sources

The rate is the index you type plus the margin, then an annuity. There is no live quote.

Page updated in 2026.