Backup Storage Size Calculator

ANA›Life Services Authority›National Calculator Authority›Backup Storage Size Calculator

.calc-container { max-width: 640px; margin: 2rem 0; padding: 1.5rem; background: #fff; border: 1px solid #ddd; border-radius: 8px; box-shadow: 0 1px 3px rgba(0,0,0,0.06); font-family: system-ui, -apple-system, sans-serif; } .calc-container h3 { font-family: Georgia, serif; font-size: 1.15rem; color: #1a1a1a; margin-bottom: 1rem; padding-bottom: 0.5rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-row { display: flex; align-items: center; gap: 0.75rem; margin-bottom: 0.75rem; flex-wrap: wrap; } .calc-row label { min-width: 160px; font-size: 0.9rem; color: #333; font-weight: 500; } .calc-row input[type="number"], .calc-row select { flex: 1; min-width: 120px; max-width: 200px; padding: 0.5rem 0.6rem; border: 1px solid #ccc; border-radius: 4px; font-size: 0.9rem; font-family: system-ui, sans-serif; color: #1a1a1a; background: #fafaf8; } .calc-row input:focus, .calc-row select:focus { outline: none; border-color: var(--ac, #3d5a80); box-shadow: 0 0 0 2px rgba(26,74,138,0.12); } .calc-row .unit { font-size: 0.82rem; color: #888; min-width: 30px; } .calc-btn { display: inline-block; margin-top: 0.5rem; padding: 0.55rem 1.5rem; background: var(--ac, #3d5a80); color: #fff; border: none; border-radius: 4px; font-size: 0.9rem; font-weight: 600; cursor: pointer; font-family: system-ui, sans-serif; } .calc-btn:hover { opacity: 0.9; } .calc-result { margin-top: 1.25rem; padding: 1rem 1.25rem; background: #f0f6fc; border-left: 3px solid var(--ac, #3d5a80); border-radius: 0 6px 6px 0; display: none; } .calc-result.visible { display: block; } .calc-result-label { font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.06em; color: #666; margin-bottom: 0.25rem; } .calc-result-value { font-size: 1.6rem; font-weight: 700; color: var(--ac, #3d5a80); } .calc-result-detail { font-size: 0.85rem; color: #555; margin-top: 0.5rem; line-height: 1.5; } .calc-note { margin-top: 1rem; font-size: 0.8rem; color: #888; font-style: italic; } .calc-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 0.75rem; margin-top: 0.75rem; } .calc-grid-item { padding: 0.6rem 0.8rem; background: #f8f9fa; border-radius: 4px; border: 1px solid #eee; } .calc-grid-item .label { font-size: 0.75rem; color: #888; text-transform: uppercase; letter-spacing: 0.04em; } .calc-grid-item .value { font-size: 1.1rem; font-weight: 600; color: #1a1a1a; } @media (max-width: 720px) { .calc-row { flex-direction: column; align-items: flex-start; gap: 0.3rem; } .calc-row label { min-width: auto; } .calc-row input[type="number"], .calc-row select { max-width: 100%; width: 100%; } .calc-grid { grid-template-columns: 1fr; } } .calc-chart { margin: 1rem 0; text-align: center; } .calc-chart svg { max-width: 100%; height: auto; } .calc-chart-legend { display: flex; flex-wrap: wrap; justify-content: center; gap: 0.6rem 1.2rem; margin-top: 0.6rem; font-size: 0.8rem; color: #555; } .calc-chart-legend span { display: inline-flex; align-items: center; gap: 0.3rem; } .calc-chart-legend i { display: inline-block; width: 10px; height: 10px; border-radius: 2px; font-style: normal; } .calc-related { max-width: 640px; margin: 2rem 0 1rem; padding: 1.25rem 1.5rem; background: #f8f9fa; border: 1px solid #e8e8e8; border-radius: 8px; } .calc-related h3 { font-family: Georgia, serif; font-size: 1rem; color: #1a1a1a; margin: 0 0 0.75rem; padding-bottom: 0.4rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-related-list { list-style: none; padding: 0; margin: 0 0 0.75rem; display: grid; grid-template-columns: 1fr 1fr; gap: 0.4rem 1.5rem; } .calc-related-list li a { font-size: 0.88rem; color: var(--ac, #3d5a80); text-decoration: none; } .calc-related-list li a:hover { text-decoration: underline; } .calc-browse-all { margin: 0.5rem 0 0; font-size: 0.9rem; font-weight: 600; } .calc-browse-all a { color: var(--ac, #3d5a80); text-decoration: none; } .calc-browse-all a:hover { text-decoration: underline; } @media (max-width: 720px) { .calc-related-list { grid-template-columns: 1fr; } }

Backup Storage Size Calculator

Estimate the total storage needed for backups considering full/incremental schedules, retention periods, compression, and deduplication ratios.

Total Data Size to Back Up (GB)

Daily Change Rate (%)

Percentage of total data that changes each day (typical: 2–10%)

Full Backup Frequency (days)

How often a full backup is taken (e.g. 7 = weekly)

Retention Period (days)

How long backups are kept before deletion

Compression Ratio

Storage saved by compression (e.g. 1.5 means data compresses to 1/1.5 of original; typical: 1.2–2.0)

Deduplication Ratio

Storage saved by deduplication (e.g. 2.0 means half the storage needed; typical: 1.5–5.0)

Number of Backup Copies (e.g. 3-2-1 rule)

Total copies including primary and offsite (3-2-1 rule recommends 3)

Storage Overhead (%)

Extra buffer for metadata, catalog, and unexpected growth (typical: 10–20%)

Calculate

function bacCalc() { var resultDiv = document.getElementById('bac-result');

var dataSize = parseFloat(document.getElementById('bac-data-size').value); var changeRate = parseFloat(document.getElementById('bac-change-rate').value); var fullFreq = parseFloat(document.getElementById('bac-full-freq').value); var retention = parseFloat(document.getElementById('bac-retention').value); var compression = parseFloat(document.getElementById('bac-compression').value); var dedup = parseFloat(document.getElementById('bac-dedup').value); var copies = parseFloat(document.getElementById('bac-copies').value); var overhead = parseFloat(document.getElementById('bac-overhead').value);

// --- Validation --- if (isNaN(dataSize) || dataSize Please enter a valid total data size greater than 0.'; return; } if (isNaN(changeRate) || changeRate 100) { resultDiv.innerHTML = 'Daily change rate must be between 0 and 100%.'; return; } if (isNaN(fullFreq) || fullFreq Full backup frequency must be a whole number ≥ 1.'; return; } if (isNaN(retention) || retention Retention period must be a whole number ≥ 1.'; return; } if (isNaN(compression) || compression Compression ratio must be ≥ 1 (1 = no compression).'; return; } if (isNaN(dedup) || dedup Deduplication ratio must be ≥ 1 (1 = no deduplication).'; return; } if (isNaN(copies) || copies Number of copies must be a whole number ≥ 1.'; return; } if (isNaN(overhead) || overhead 100) { resultDiv.innerHTML = 'Storage overhead must be between 0 and 100%.'; return; }

// --- Core Calculations ---

// Number of full backups within retention window var numFullBackups = Math.ceil(retention / fullFreq);

// Number of incremental backups within retention window // Each cycle of fullFreq days has (fullFreq - 1) incremental days // Total incremental days = retention - numFullBackups (one full per cycle) var numIncrementals = retention - numFullBackups; if (numIncrementals ';

function row(label, value, highlight) {
var style = highlight
? 'style="font-weight:bold;background:#f0f7ff;border-top:2px solid #3b82f6;"'
'style="border-bottom:1px solid #e5e7eb;"'; return '' + label + '' + value + ''; }

html += row('Full backups in retention window', numFullBackups + ' backup(s)'); html += row('Incremental backups in retention window', numIncrementals + ' backup(s)'); html += row('Daily incremental data size', dailyChangeGB.toFixed(2) + ' GB'); html += row('Raw full backup storage', rawFullStorage.toFixed(2) + ' GB'); html += row('Raw incremental backup storage', rawIncrementalStorage.toFixed(2) + ' GB'); html += row('Total raw storage (before reduction)', rawTotalStorage.toFixed(2) + ' GB'); html += row('Combined reduction factor (compression × dedup)', reductionFactor.toFixed(2) + '×'); html += row('Storage after compression & deduplication', reducedStorage.toFixed(2) + ' GB'); html += row('Storage after overhead buffer', storageWithOverhead.toFixed(2) + ' GB'); html += row('Number of copies', copies); html += row('Total required storage (' + copies + ' cop' + (copies === 1 ? 'y' : 'ies') + ')', totalStorage.toFixed(2) + ' GB (' + totalStorageTB.toFixed(3) + ' TB)', true); html += '';

// Practical recommendation var recommended = Math.ceil(totalStorage / 100) * 100; html += ''; html += 'Recommended provisioned storage: ' + recommended + ' GB (' + (recommended/1024).toFixed(2) + ' TB) — rounded up to nearest 100 GB for practical allocation.'; html += '

';

resultDiv.innerHTML = html; }

#### Formulas Used

Number of full backups = ⌈Retention Days ÷ Full Backup Frequency⌉

Number of incremental backups = Retention Days − Number of Full Backups

Daily incremental size = Total Data Size × (Daily Change Rate ÷ 100)

Raw full backup storage = Number of Full Backups × Total Data Size

Raw incremental storage = Number of Incrementals × Daily Incremental Size

Total raw storage = Raw Full Storage + Raw Incremental Storage

Reduction factor = Compression Ratio × Deduplication Ratio

Reduced storage = Total Raw Storage ÷ Reduction Factor

Storage with overhead = Reduced Storage × (1 + Overhead% ÷ 100)

Total required storage = Storage with Overhead × Number of Copies

#### Assumptions & References

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References

Related Authorities

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