B Tree Index Capacity Calculator
Estimate the minimum height and page count of an ideal uniformly filled B+ tree index.
YOUR CALCULATION
Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Use the same key/pointer widths at every level and aggregate parent pages until one root remains.
Leaf capacity=floor((page−header) fill/(key+pointer)); internal children=floor(((page−header) fill+key)/(key+pointer))
Worked example
With leaf capacity 100 and branching 100, one million records need 10000 leaves, 100 parents and one root: three levels.
Assumptions and input details
Ideal fixed-size keys and entries, no prefix compression, variable payload, deleted pages, splits, cache or actual database engine policy. Occupancy is a planning assumption. Header must leave capacity for at least two entries.
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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