Workout Math Utilities: 1RM and Volume Calculations

FocusFlow’s workout math utilities, located in src/utils/workoutMath.ts, provide pure functions for estimating one-rep maxima and generating percentage-based load tables. These functions power the in-app 1RM calculator and the progressive overload suggestions shown to both coaches and athletes during session planning.

All three functions are fully tree-shakeable exports. Import only the functions you need to keep client bundles lean.

`calculate1RM`

Calculates the estimated one-repetition maximum (1RM) from a sub-maximal lift using either the Epley or Brzycki formula. This is the foundational building block used by both getRMPercentage and generateRMTable.

export function calculate1RM(
  weight: number,
  reps: number,
  formula: 'epley' | 'brzycki' = 'epley'
): number

Parameters

Parameter	Type	Description
`weight`	`number`	Load lifted in kg (or lbs — unit is consistent throughout)
`reps`	`number`	Number of repetitions performed at that load
`formula`	`'epley' \| 'brzycki'`	Formula to use (defaults to `'epley'`)

Return value

The estimated 1RM rounded to 1 decimal place. Returns 0 if weight ≤ 0 or reps ≤ 0. Returns weight unchanged when reps === 1 (the lift itself is the 1RM).

Formulas

Epley:

1RM = weight × (1 + reps / 30)

Brzycki:

1RM = weight / (1.0278 − 0.0278 × reps)

Brzycki’s denominator approaches zero as reps approach 37. When reps ≥ 37, FocusFlow automatically falls back to the Epley formula to avoid a division-by-zero or negative result.

Usage example

import { calculate1RM } from './utils/workoutMath';

// Athlete lifted 80 kg for 5 reps
const oneRM = calculate1RM(80, 5, 'epley');
// => 93.3

// Same lift using Brzycki
const oneRMBrzycki = calculate1RM(80, 5, 'brzycki');
// => 94.6

// Edge cases
calculate1RM(0, 5, 'epley');  // => 0  (invalid weight)
calculate1RM(80, 1, 'epley'); // => 80 (single rep: already the 1RM)

`getRMPercentage`

Calculates the target training load for a given percentage of a known 1RM. Use this to prescribe warm-up sets, back-off sets, or any intensity zone.

export function getRMPercentage(
  oneRM: number,
  percentage: number
): number

Parameters

Parameter	Type	Description
`oneRM`	`number`	The athlete’s one-rep max (from `calculate1RM` or a tested max)
`percentage`	`number`	Desired intensity as a whole number (e.g. `80` for 80%)

Return value

oneRM × (percentage / 100), rounded to 1 decimal place. Returns 0 if either argument is ≤ 0.

Usage example

import { calculate1RM, getRMPercentage } from './utils/workoutMath';

const oneRM = calculate1RM(80, 5, 'epley'); // 93.3

// Target weight for an 80% intensity set
const targetWeight = getRMPercentage(oneRM, 80);
// => 74.6

// Warm-up set at 60%
const warmUp = getRMPercentage(oneRM, 60);
// => 56.0

Pair getRMPercentage with the intensity field on RoutineExercise to auto-fill suggested weights when the coach prescribes a load as a percentage of the athlete’s last tested 1RM.

`generateRMTable`

Generates a full 12-entry repetition-maximum table from a single sub-maximal effort. Each entry maps a rep count (1–12) to the corresponding recommended weight and percentage of 1RM, using the standard strength-training percentage map.

export function generateRMTable(
  weight: number,
  reps: number,
  formula: 'epley' | 'brzycki' = 'epley'
): { reps: number; weight: number; percentage: number }[]

Parameters

Parameter	Type	Description
`weight`	`number`	Load used in the reference set
`reps`	`number`	Reps performed at that load
`formula`	`'epley' \| 'brzycki'`	Formula used to estimate the 1RM (defaults to `'epley'`)

Return value

An array of 12 objects { reps, weight, percentage } covering rep counts 1 through 12. Returns an empty array [] if the computed 1RM is ≤ 0.

Percentage map

The function uses the following standard resistance-training percentage map:

Reps	% of 1RM
1	100%
2	95%
3	93%
4	90%
5	87%
6	85%
7	83%
8	80%
9	77%
10	75%
11	72%
12	70%

Example output for a 100 kg 1RM

When the estimated 1RM is 100 kg, generateRMTable produces the following load table:

Reps	% of 1RM	Target Weight (kg)
1	100%	100.0
2	95%	95.0
3	93%	93.0
4	90%	90.0
5	87%	87.0
6	85%	85.0
7	83%	83.0
8	80%	80.0
9	77%	77.0
10	75%	75.0
11	72%	72.0
12	70%	70.0

Usage example

import { generateRMTable } from './utils/workoutMath';

// Athlete squatted 90 kg for 6 reps
const table = generateRMTable(90, 6, 'epley');

// table[0] => { reps: 1,  percentage: 100, weight: 105.9 }
// table[4] => { reps: 5,  percentage: 87,  weight: 92.1  }
// table[7] => { reps: 8,  percentage: 80,  weight: 84.7  }
// table[11]=> { reps: 12, percentage: 70,  weight: 74.1  }

Show Full source implementation

export function generateRMTable(
  weight: number,
  reps: number,
  formula: 'epley' | 'brzycki' = 'epley'
): { reps: number; weight: number; percentage: number }[] {
  const oneRM = calculate1RM(weight, reps, formula);
  if (oneRM <= 0) return [];

  const repPctMap = [
    { reps: 1,  percentage: 100 },
    { reps: 2,  percentage: 95  },
    { reps: 3,  percentage: 93  },
    { reps: 4,  percentage: 90  },
    { reps: 5,  percentage: 87  },
    { reps: 6,  percentage: 85  },
    { reps: 7,  percentage: 83  },
    { reps: 8,  percentage: 80  },
    { reps: 9,  percentage: 77  },
    { reps: 10, percentage: 75  },
    { reps: 11, percentage: 72  },
    { reps: 12, percentage: 70  },
  ];

  return repPctMap.map((item) => ({
    reps: item.reps,
    percentage: item.percentage,
    weight: Math.round(oneRM * (item.percentage / 100) * 10) / 10,
  }));
}

Data Types

Firebase & Storage

Utilities

Workout Math Utilities: 1RM and Volume Calculations

`calculate1RM`

Parameters

Return value

Formulas

Usage example

`getRMPercentage`

Parameters

Return value

Usage example

`generateRMTable`

Parameters

Return value

Percentage map

Example output for a 100 kg 1RM

Usage example

Build docs developers (and LLMs) love

Data Types

Firebase & Storage

Utilities

Documentation Index

​calculate1RM

​Parameters

​Return value

​Formulas

​Usage example

​getRMPercentage

​Parameters

​Return value

​Usage example

​generateRMTable

​Parameters

​Return value

​Percentage map

​Example output for a 100 kg 1RM

​Usage example

Build docs developers (and LLMs) love

`calculate1RM`

Parameters

Return value

Formulas

Usage example

`getRMPercentage`

Parameters

Return value

Usage example

`generateRMTable`

Parameters

Return value

Percentage map

Example output for a 100 kg 1RM

Usage example