Strength Standards API & Widgets for Developers

FitnessVolt Strength Standards API (FVSS)

The FitnessVolt Strength Standards API serves verified competition percentiles and self-reported gym percentiles as separate, labeled populations.

FVSS v1 is a free, versioned, read-only, CORS-enabled JSON API. No key, no signup. It serves two populations and keeps them strictly separate: verified percentiles built from over 2.5 million processed OpenPowerlifting competition results (squat, bench press, deadlift; Raw), and gym percentiles from the Symmetric Strength self-reported dataset. The two are never blended into a composite, and every response labels its source and sample size.

Base URL: https://fitnessvolt.com/wp-json/fvss/v1 · API version 1.0.0 · data snapshot 2026-06-09 · OpenAPI 3.0 document · methodology

Endpoints

Five endpoints, versioned under fvss/v1. Every standards and percentile response carries source, source_label, sample sizes, unit, methodology_url, attribution, api_version, and data_version.

GET /standards

Capability document: supported lifts per source, sexes, units, formats, age brackets (gym only), versions, rate limits, and the attribution contract.

curl

curl "https://fitnessvolt.com/wp-json/fvss/v1/standards"

GET /standards/{lift}

Standards for one lift from ONE explicit source. source is required and never defaulted: there is no blending and no composite. format=table lists every stored weight class; format=summary (needs bodyweight) returns the closest cohort; format=curve (verified only) returns the 18-bin distribution.

lift: Path segment. verified: squat, bench-press, deadlift. gym: the stored Symmetric Strength slugs listed by GET /standards.
sex: Required. male | female.
source: Required. verified | gym. Never defaulted, never blended.
bodyweight: Required for format=summary and format=curve. In the requested unit.
unit: lb | kg. Default lb.
format: summary | table | curve. Default summary.

curl

curl "https://fitnessvolt.com/wp-json/fvss/v1/standards/bench-press?format=table&sex=male&source=verified&unit=lb"

POST /percentile

Dual percentile for one set: the verified competition percentile (SBD lifts) and the self-reported gym percentile (supported lifts), each with its own tier and sample size, never merged. reps > 1 estimates the 1RM server-side with the same five-formula average the on-site calculators use, flagged e1rm_is_estimated.

lift: Required. Lift slug.
weight: Required. Weight lifted, in unit.
reps: 1-12. Default 1.
bodyweight: Required. In unit.
sex: Required. male | female.
unit: lb | kg. Default lb.
age: Optional, 10-90. Refines the gym cohort.

curl

curl -X POST "https://fitnessvolt.com/wp-json/fvss/v1/percentile" -H "Content-Type: application/json" -d '{"lift":"bench-press","weight":225,"reps":5,"bodyweight":200,"sex":"male","unit":"lb"}'

GET /fvcp/{lift}

The FVCP (FitnessVolt Competition Percentile) namespace: verified OpenPowerlifting SBD competition data ONLY (squat, bench-press, deadlift; Raw). Full percentile tables for every stored weight class, both sexes. Any other lift returns an honest 404.

lift: Path segment. squat | bench-press | deadlift.
unit: lb | kg. Default lb.

curl

curl "https://fitnessvolt.com/wp-json/fvss/v1/fvcp/deadlift?unit=kg"

GET /openapi

The machine-readable OpenAPI 3.0 document for this namespace. Point your client generator or LLM tool-use schema at it.

curl

curl "https://fitnessvolt.com/wp-json/fvss/v1/openapi"

Code Samples

JavaScript (fetch)

JS

// Dual percentile for a 225 lb x 5 bench at 200 lb bodyweight.
fetch('https://fitnessvolt.com/wp-json/fvss/v1/percentile', {
  method: 'POST',
  headers: { 'Content-Type': 'application/json' },
  body: JSON.stringify({
    lift: 'bench-press', weight: 225, reps: 5,
    bodyweight: 200, sex: 'male', unit: 'lb'
  })
})
  .then(function (r) { return r.json(); })
  .then(function (d) {
    // d.verified and d.gym are separate, labeled populations.
    if (d.verified) { console.log('Verified competition: ' + d.verified.percentile + 'th (n=' + d.verified.sample_size + ')'); }
    if (d.gym)      { console.log('Self-reported gym:    ' + d.gym.percentile + 'th (n=' + d.gym.sample_size + ')'); }
    console.log('Attribution required: ' + d.attribution.text);
  });

PHP (wp_remote_get)

PHP

<?php
// Verified bench press standards table (WordPress).
$response = wp_remote_get(
	'https://fitnessvolt.com/wp-json/fvss/v1/standards/bench-press?format=table&sex=male&source=verified&unit=lb'
);
if ( ! is_wp_error( $response ) && 200 === wp_remote_retrieve_response_code( $response ) ) {
	$data = json_decode( wp_remote_retrieve_body( $response ), true );
	foreach ( $data['weight_classes'] as $row ) {
		// $row['weight_class_label'], $row['sample_size'], $row['percentiles']['p50'] ...
	}
	// Keep $data['attribution']['html'] visible wherever you show the numbers.
}

Python (requests)

Python

import requests

# Verified-only FVCP tables for the deadlift, in kg.
resp = requests.get('https://fitnessvolt.com/wp-json/fvss/v1/fvcp/deadlift', params={'unit': 'kg'}, timeout=10)
resp.raise_for_status()
data = resp.json()

for wc in data['sexes']['male']['weight_classes']:
    print(wc['weight_class_label'], wc['sample_size'], wc['percentiles']['p50'])

# data['attribution']['text'] must stay visible with the numbers.
print(data['attribution']['text'])

Rate Limits & Caching

60 requests per 60 seconds, per IP, per endpoint group. Exceeding it returns HTTP 429 with a Retry-After header.
GET responses send Cache-Control: public, max-age=3600. Cache on your side; the underlying percentile tables change only when the data snapshot is rebuilt (current snapshot: 2026-06-09).
All endpoints send Access-Control-Allow-Origin: *, so they are callable from any origin, browser or server.
Cohorts under 30 samples are omitted rather than served with an unreliable percentile.
Need more than the per-IP limit? See the attribution tiers below.

Attribution & Licensing

Every response carries an attribution object with ready-made text and HTML. Three tiers:

Tier	Who it is for	Terms
Free	Any site, app, tool, or article within the per-IP rate limit.	Keep a visible attribution link ("Powered by FitnessVolt Strength Standards" or the `attribution.html` from the response) wherever the data is shown. The embeddable widgets satisfy this automatically.
Registered high-volume	Projects that need sustained traffic above the per-IP limit.	Free with the same visible attribution; contact us so we can allowlist your usage instead of rate limiting it.
Commercial, no attribution	Commercial products that cannot show the link.	By arrangement only. Contact FitnessVolt via the contact page.

Cite the underlying sources where relevant: the OpenPowerlifting dataset (verified competition results) and the Symmetric Strength dataset (self-reported gym lifts). Citation formats live on the open data hub.

Embeddable Widgets (live)

Three copy-paste widgets, one script tag. Vanilla JS, no framework, no build step, styles fully scoped so they cannot fight your page. The script derives the API base from its own URL, so the same snippet works on any site. Each widget renders the required "Powered by FitnessVolt Strength Standards" link and labels every number with its population and sample size. The widgets below are LIVE, served by the same snippet you would paste.

1. Standards table

One lift, one source, every stored weight class. Configure with data-lift, data-sex (male | female), data-source (verified | gym), data-unit (lb | kg).

HTML

<div class="fvss-widget" data-widget="standards-table"
     data-lift="bench-press" data-sex="male"
     data-source="verified" data-unit="lb"></div>
<script async src="https://fitnessvolt.com/wp-content/plugins/rpe-training/assets/widgets/fvss-widgets.js?ver=1781034779"></script>

Live:

2. Mini percentile calculator

Weight, reps, bodyweight, sex in; both labeled percentiles out, with a link to the full FitnessVolt result page. Configure with data-lift and data-unit.

HTML

<div class="fvss-widget" data-widget="percentile-calc"
     data-lift="bench-press" data-unit="lb"></div>
<script async src="https://fitnessvolt.com/wp-content/plugins/rpe-training/assets/widgets/fvss-widgets.js?ver=1781034779"></script>

Live:

3. Free program CTA

Maxes in, deep link out to the free FitnessVolt program generator (the maxes travel as URL parameters; nothing is written to our API). Configure with data-program (a program slug from /rpe-training/programs/), data-unit, and optional data-heading.

HTML

<div class="fvss-widget" data-widget="program-cta"
     data-program="fitnessvolt-autoregulated" data-unit="lb"></div>
<script async src="https://fitnessvolt.com/wp-content/plugins/rpe-training/assets/widgets/fvss-widgets.js?ver=1781034779"></script>

Live:

The attribution link is part of the free license and is not configurable. Include the script once per page; it initializes every .fvss-widget mount it finds (SPA hosts can call window.FVSSWidgets.init() after injecting new mounts).

Version & Changelog

The namespace is versioned (fvss/v1). Breaking changes ship as a new namespace; fvss/v1 stays stable. Additive fields may appear without notice, so parse responses tolerantly.

Date	API	Change
2026-06-09	`1.0.0`	Initial public release: capability document, per-lift standards (summary, table, curve), dual percentile, verified-only FVCP namespace, OpenAPI document, embeddable widgets v1. Data snapshot 2026-06-09 (post-remediation OpenPowerlifting percentile table; Symmetric Strength aggregates).

Questions or higher-volume needs: contact FitnessVolt. See also the open data hub and the methodology.

Strength Standards API & Widgets

FitnessVolt Strength Standards API (FVSS)

Endpoints

Code Samples

JavaScript (fetch)

PHP (wp_remote_get)

Python (requests)

Rate Limits & Caching

Attribution & Licensing

Embeddable Widgets (live)

1. Standards table

2. Mini percentile calculator

3. Free program CTA

Version & Changelog

Topics

More