Net Interest Margin (NIM) Calculator & ALM Banking Lab
Model commercial bank Net Interest Margin, net interest spread, earning asset yields, rate sensitivity gap, and NII interest rate shock sensitivity.
Bank Asset-Liability Management (ALM) Presets
Bank Balance Sheet & Income Inputs
Enter balance sheet averages and annual interest cash flows in thousands ($000).
1. Earning Assets & Interest Income
2. Interest-Bearing Liabilities & Funding Costs
3. ALM Repricing Gap & Rate Shock
Asset-Liability Management (ALM) Diagnostic
| Net Interest Income (NII): | $380,000,000 | Gross Interest Income minus Interest Expense |
| Average Yield on Earning Assets ($y_A$): | 5.00% | Interest Income / Average Earning Assets |
| Average Cost of Interest Funds ($c_L$): | 2.50% | Interest Expense / Interest-Bearing Liabilities |
| Free Non-Interest Funding Lift: | +0.54% | NIM minus Spread (benefit of free core deposits & equity) |
| Gap Ratio (RSA / RSL): | 1.50x | > 1.0 indicates Asset Sensitivity |
| Shocked Net Interest Margin: | 3.24% | Projected NIM after +100 bps rate shock |
Banking Sensitivity Analysis Matrices
Sensitivity Grid 1: Asset Yield vs Cost of Funds (Net Interest Margin %)
Evaluates how shifts in loan pricing yields and deposit funding costs compress or expand the bank's NIM.
Sensitivity Grid 2: Rate Shock (bps) vs Repricing Gap (ΔNII $000)
Projects annual Net Interest Income dollar variance under parallel rate hikes and rate cuts across ALM gap postures.
Worked Calculation & Mathematical Specification
Net Interest Margin (NIM) is the foundational profitability benchmark in financial intermediation. Because banks borrow money at short-term rates and lend at longer-term rates, managing the spread between asset yields and liability costs while controlling repricing gaps is the central task of Bank Treasury and ALM committees.
$$\text{Net Interest Income (NII)} = \text{Interest Income} - \text{Interest Expense}$$
$$\text{Net Interest Margin (NIM)} = \frac{\text{Net Interest Income}}{\text{Average Earning Assets}} \times 100\%$$
$$\text{Gross Earning Asset Yield } (y_A) = \frac{\text{Interest Income}}{\text{Average Earning Assets}} \times 100\%$$
$$\text{Cost of Interest-Bearing Funds } (c_L) = \frac{\text{Interest Expense}}{\text{Average Interest-Bearing Liabilities}} \times 100\%$$
$$\text{Net Interest Spread} = y_A - c_L$$
$$\text{Rate-Sensitivity Repricing Gap (GAP)} = \text{Rate-Sensitive Assets (RSA)} - \text{Rate-Sensitive Liabilities (RSL)}$$
$$\Delta \text{NII from Rate Shock} = \text{GAP} \times \left(\frac{\Delta \text{bps}}{10,000}\right)$$
Step-by-Step Calculation Walkthrough (Current Simulation State)
| Step | Metric Operation | Formula | Calculation | Result |
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ALM Strategic Management Takeaways
- The Free Funding Advantage: When a bank has a substantial base of non-interest demand deposit accounts (DDA), its NIM consistently exceeds its Net Interest Spread. In our baseline model, free deposits and equity provide a +0.54% yield lift to NIM.
- Asset-Sensitive Profiles: Commercial banks with large commercial loan books (SOFR/Prime-indexed floating credit) benefit automatically from Fed rate hikes because assets reprice instantaneously while retail deposit betas lag.
- Liability-Sensitive Hazards: Thrifts and regional banks heavily invested in long-duration fixed-rate residential mortgages funded by high-beta certificates of deposit face severe margin squeeze and unrealized bond portfolio losses during aggressive monetary tightening cycles.
Net Interest Margin & ALM Knowledge Check Quiz
Test your mastery of bank interest margins, asset-liability sensitivity gaps, and monetary policy rate transmission.
1. Why is a commercial bank's Net Interest Margin (NIM) almost always higher than its Net Interest Spread?
2. If a bank has $8.0B in rate-sensitive assets (RSA) and $5.0B in rate-sensitive liabilities (RSL), what happens to its Net Interest Income if interest rates rise by 100 bps (+1.00%)?
3. What is a "liability-sensitive" bank posture?
4. What does "deposit beta" measure in banking treasury operations?
Frequently Asked Questions
What is Net Interest Margin (NIM) and how is it calculated?
Net Interest Margin (NIM) is the primary profitability metric for commercial banks and depository institutions. It measures the net investment income generated from loans and securities relative to the total volume of earning assets: NIM = (Interest Income - Interest Expense) / Average Earning Assets. It reflects how efficiently a bank deploys deposits and borrowings into income-generating loans.
What is the difference between Net Interest Margin (NIM) and Net Interest Spread?
Net Interest Spread is the pure difference between the average yield earned on assets and the average interest rate paid on liabilities: Spread = (Interest Income / Earning Assets) - (Interest Expense / Interest-Bearing Liabilities). NIM is typically higher than Spread because a bank funds a portion of its earning assets with free, non-interest-bearing funds (such as non-interest demand deposits and shareholder equity capital).
What is an Interest Rate Sensitivity Gap in bank asset-liability management (ALM)?
The Interest Rate Sensitivity Gap (or GAP) measures the mismatch between assets and liabilities repricing within a given time bucket: GAP = Rate-Sensitive Assets (RSA) - Rate-Sensitive Liabilities (RSL). A positive gap (Asset-Sensitive) means more assets reprice than liabilities when rates change; a negative gap (Liability-Sensitive) means liabilities reprice faster, exposing the bank to margin compression during rate hikes.
How do Federal Reserve rate hikes affect asset-sensitive versus liability-sensitive banks?
When central banks raise policy rates, an asset-sensitive bank (RSA > RSL) experiences an expansion in Net Interest Income (NII) and NIM because floating-rate loans reprice upward faster than deposit costs. Conversely, a liability-sensitive bank (RSL > RSA) suffers margin compression because its funding costs rise faster than yields on its fixed-rate loans and securities.