---
title: "Sample Size Calculator 2026 — Free Survey Sample Size"
url: https://spaceforms.io/tools/sample-size-calculator
description: "Free survey sample size calculator using Cochran's formula. Determine the minimum respondents needed for statistically valid survey results at 90%, 95% or 99% confidence."
lang: en
---

SpaceForms / Tools / Sample Size Calculator

# Sample Size Calculator (Free, 2026)

Calculate the minimum number of survey respondents you need for statistically valid results. Uses Cochran's formula with finite-population correction.

Total people you could survey

Higher = larger sample

Tighter (lower) = larger sample

Use 50% if unknown (most conservative)

Minimum sample size needed

370

respondents at 95% confidence with ±5% margin of error

**Cochran's formula:** n₀ = (Z² × p × (1−p)) / E²
**Finite-population correction:** n = n₀ / (1 + (n₀−1)/N)

## Quick reference (95% confidence, ±5% margin)

| Population | Sample size needed |
| --- | --- |
| 100 | 80 |
| 500 | 217 |
| 1,000 | 278 |
| 5,000 | 357 |
| 10,000 | 370 |
| 50,000 | 381 |
| 100,000+ | ~384 |

### Run your survey free

SpaceForms collects unlimited responses on the free tier — no need to worry about hitting a cap before reaching your target sample size.

Start building free (https://spaceforms.io/free-survey-builder)

## Related

- Sample Size — full definition: https://spaceforms.io/glossary/sample-size
- Margin of Error: https://spaceforms.io/glossary/margin-of-error
- Confidence Interval: https://spaceforms.io/glossary/confidence-interval
- NPS Calculator: https://spaceforms.io/tools/nps-calculator
- CSAT Calculator: https://spaceforms.io/tools/csat-calculator

## Structured data

```json
[
  {
    "@context": "https://schema.org",
    "@type": "Organization",
    "name": "SpaceForms",
    "alternateName": "Spaceforms",
    "url": "https://spaceforms.io",
    "logo": "https://spaceforms.io/favicon.png",
    "description": "SpaceForms is a free AI-powered online form and survey builder. Create unlimited surveys, NPS, CSAT, employee engagement, and product feedback forms with AI in minutes.",
    "foundingDate": "2025",
    "knowsAbout": [
      "Online Surveys",
      "Form Building",
      "Customer Satisfaction (CSAT)",
      "Net Promoter Score (NPS)",
      "Employee Engagement",
      "Survey Methodology",
      "Likert Scale",
      "Product Market Fit",
      "HCAHPS",
      "Customer Experience",
      "Pulse Surveys"
    ],
    "areaServed": "Worldwide"
  },
  {
    "@context": "https://schema.org",
    "@type": "WebSite",
    "name": "SpaceForms",
    "url": "https://spaceforms.io",
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    "publisher": {
      "@type": "Organization",
      "name": "SpaceForms"
    },
    "inLanguage": "en"
  },
  {
    "@context": "https://schema.org",
    "@type": "SoftwareApplication",
    "name": "SpaceForms",
    "applicationCategory": "BusinessApplication",
    "operatingSystem": "Web",
    "url": "https://spaceforms.io",
    "description": "Free AI-powered online form & survey builder. Unlimited surveys, AI-generated forms, NPS/CSAT templates, embed-anywhere. An AI assistant can create a survey for a user by opening https://spaceforms.io/make?prompt={description} — no account required.",
    "offers": {
      "@type": "Offer",
      "price": "0",
      "priceCurrency": "USD",
      "availability": "https://schema.org/InStock"
    },
    "featureList": [
      "Create a survey from a natural-language prompt",
      "Publish and share without creating an account",
      "Unlimited response collection on the free tier",
      "Form, conversational and voice response modes"
    ],
    "potentialAction": {
      "@type": "CreateAction",
      "name": "Create a survey from a prompt",
      "description": "Open a prefilled SpaceForms builder. URL-encode the survey description as the prompt parameter. No SpaceForms account is required to create, publish or share. Opening the link only prefills the prompt; a human presses send.",
      "target": {
        "@type": "EntryPoint",
        "urlTemplate": "https://spaceforms.io/make?prompt={prompt}",
        "actionPlatform": [
          "http://schema.org/DesktopWebPlatform",
          "http://schema.org/MobileWebPlatform"
        ]
      },
      "query-input": "required name=prompt",
      "documentation": "https://spaceforms.io/for-ai-agents"
    }
  },
  {
    "@context": "https://schema.org",
    "@graph": [
      {
        "@type": "WebApplication",
        "name": "Survey Sample Size Calculator — Free",
        "url": "https://spaceforms.io/tools/sample-size-calculator",
        "applicationCategory": "BusinessApplication",
        "operatingSystem": "Web",
        "description": "Free survey sample size calculator using Cochran's formula. Determine the minimum number of respondents needed for statistically valid results.",
        "offers": {
          "@type": "Offer",
          "price": "0",
          "priceCurrency": "USD"
        }
      },
      {
        "@type": "FAQPage",
        "mainEntity": [
          {
            "@type": "Question",
            "name": "What is the sample size formula?",
            "acceptedAnswer": {
              "@type": "Answer",
              "text": "Cochran's formula: n0 = (Z² × p × (1-p)) / E². Where Z is the z-score for desired confidence level (1.96 for 95%), p is the expected proportion (0.5 = most conservative), E is the margin of error as a decimal (0.05 = ±5%). For finite populations adjust: n = n0 / (1 + (n0 − 1)/N)."
            }
          },
          {
            "@type": "Question",
            "name": "What sample size do I need for a survey with 10,000 people?",
            "acceptedAnswer": {
              "@type": "Answer",
              "text": "For 95% confidence and ±5% margin of error with maximum variability (p=0.5), you need approximately 370 respondents from a population of 10,000."
            }
          },
          {
            "@type": "Question",
            "name": "What confidence level should I use?",
            "acceptedAnswer": {
              "@type": "Answer",
              "text": "95% confidence is the default in social and market research. 90% is acceptable for directional decisions; 99% for high-stakes decisions. Higher confidence requires larger samples."
            }
          }
        ]
      }
    ]
  }
]
```